Health Equity: Center-Based Early Childhood Education

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Summary of CPSTF Finding

The Community Preventive Services Task Force (CPSTF) recommends center-based early childhood education programs (ECE) to improve educational outcomes that are associated with long-term health as well as social- and health-related outcomes. Economic evidence indicates there is a positive return on investment in early childhood education. The benefits from students' future earnings gains alone exceed program costs.

If targeted to low-income or racial and ethnic minority communities, ECE programs are likely to reduce educational achievement gaps, improve the health of these student populations, and promote health equity.

Intervention

Center-based early childhood education programs aim to improve the cognitive or social development of children ages 3 or 4 years.

Programs must include an educational component that addresses one or more of the following: literacy, numeracy, cognitive development, socio-emotional development, and motor skills.
Programs may offer additional components including recreation, meals, health care, parental supports, and social services.
Programs may enroll children before they are 3 years of age.

CPSTF Finding and Rationale Statement

Read the full CPSTF Finding and Rationale Statement pdf icon [PDF - 639 kB] for details including implementation issues, possible added benefits, potential harms, and evidence gaps.

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What the CPSTF Found

About The Systematic Review

The CPSTF finding is based on evidence from a 2014 meta-analysis of 49 studies of center-based preschool programs for low-income children ages 3 and 4 years (Kay & Pennucci, 2014). The report was published by the Washington State Institute for Public Policy—a non-partisan research institution that evaluates programs for the Washington State legislature to inform policy decisions. The meta-analysis (search period through November 2013) met Community Guide systematic review standards in terms of intervention definition, outcome assessment, study design and execution evaluation, and synthesis of effect estimates.

This finding replaces the 2000 CPSTF finding on Promoting Health Equity Through Education Programs and Policies: Comprehensive, Center-Based Programs for Children of Low-Income Families to Foster Early Childhood Development pdf icon [PDF - 315 kB].

This review was conducted on behalf of the CPSTF by a team of specialists in systematic review methods, and in research, practice and policy related to the use of educational interventions for the promotion of health equity.

Context

Children in low-income families often experience delays in language and other development by the age of three. Compensating for these delays before children begin regular schooling may provide them with equal opportunities for lifelong employment, income, and health.

Summary of Results

Detailed results from the systematic review are available in the CPSTF Finding and Rationale Statement [PDF - 639 kB].

This review included evaluations of three types of early childhood education programs:

State and district programs
The federal Head Start program
Model programs such as the Perry Pre-School and Abecedarian programs (Campbell et al., 2002; Schweinhart et al., 2005)

Education-related outcomes*:

Test scores: mean increase of 0.29 standard deviations (27 study arms)
High school graduation: mean increase of 0.20 standard deviations (7 study arms)
Grade retention (in which children are held back from the next grade because they have not succeeded in required learning): mean decrease of 0.23 standard deviations (12 study arms)
Assignment to special education (in which children are taken out of the standard learning track and assigned to receive extra attention because of learning difficulties): mean decrease of 0.28 standard deviations (6 study arms)

Social- and Health-related outcomes*:

Crime rates: mean decrease of 0.23 standard deviations (5 study arms)
Teen birth rates: mean decrease of 0.46 standard deviations (3 study arms)
Self-Regulation: mean increase of 0.21 standard deviations (5 study arms)
Emotional development: mean increase of 0.04 standard deviations (7 study arms)

*While findings for the three ECE types were reported separately in their meta-analysis, authors Kay and Pennucci aggregated the results for this systematic review.

Results for each program type:

All effects were in a favorable direction for each program type (for which they were evaluated), but not all effects were statistically significant at the 0.05 level.
- Standardized achievement tests – significant beneficial effects were found for all three program types:
  - State and district: 0.32 standard deviations
  - Head Start: 0.17 standard deviations
  - Model: 0.57 SD standard deviations
- High school graduation – a statistically significant positive effect was found for Head Start programs, but not for the other program types:
  - State and district: 0.23 standard deviations
  - Head Start: 0.18 standard deviations
  - Model: 0.31 SD standard deviations
- Grade retention or assignment to special education – non-significant effects were found for all program types:
  - State and district: ‑0.39 standard deviations
  - Head Start: ‑0.08 standard deviations
  - Model: ‑0.46 standard deviations
- Assignment to special education – non-significant favorable effects were found for state and district and model program types, and this outcome was not evaluated for Head Start:
  - State and district: ‑0.12 standard deviations
  - Model: ‑0.47 standard deviations
- Crime – non-significant effects were found for all program types:
  - State and district: ‑0.25 standard deviations
  - Head Start: ‑0.18 standard deviations
  - Model: ‑0.32 standard deviations
- Teen birth rates – no studies of state and district programs evaluated this outcome, and non-significant effects were found for the other two program types:
  - Head Start: ‑0.47 standard deviations
  - Model: ‑0.44 standard deviations
- Self-regulation – a statistically significant effect was found for state and district programs, a non-significant benefit was shown for Head Start, and no studies of model programs evaluated this outcome:
  - State and district: ‑0.23 standard deviations
  - Head Start: 0.16 standard deviations
- Emotional development – effects were negligible and statistically non-significant for state and district programs and Head Start programs, and no studies of model programs evaluated this outcome
  - State and district: 0.04 standard deviations
  - Head Start: 0.03 standard deviations
Persistence of program effects:
- Effects of early childhood programs persisted on scores of standardized achievement tests and other cognitive tests. A statistically significant program benefit remained until students were 9 years old; effects slowly declined in later years.
Effect modification:
- Data were insufficient to determine the most effective class size, hours, duration, program foci, or the benefit of additional program components (e.g., health care, parental involvement, or meals).

Summary of Economic Evidence

Detailed results from the systematic review are available in the CPSTF Finding and Rationale Statement [PDF - 639 kB].

Economic evidence indicates there is a positive return on investment in early childhood education. The benefits from students’ future earnings gains alone exceed program costs.

The economic review included 7 studies from the U.S. with additional analysis from one of the studies. All monetary values reported are in 2014 U.S. dollars.

The median benefit-to-cost ratio from eleven estimates of students’ future earnings gains was 3.39:1, suggesting that for every $1 invested in the program, there was a return of $3.39 in earnings gains alone.
The overall median benefit-to-cost ratio from seven estimates reported in four studies and the national-level analysis was 4.19:1.
The benefits were greater than the costs for all three types of early childhood education programs including state and district, federal Head Start, and model programs.
Intervention cost estimates were based on funding per participant.
Intervention benefit estimates, both short and long term, included some or all of the following major components:
- Increases in maternal employment and income
- Reductions in crime, welfare dependency, and child abuse and neglect
- Savings in remedial education and child care costs
- Improvement in health outcomes associated with education
- Earnings gains associated with high school graduation

Applicability

Based on the available evidence, ECE programs directed toward low-income or racial and ethnic minority communities are expected to advance health equity.
While the meta-analysis did not include studies of programs directed to higher income or predominantly white communities, programs in these communities are generally of higher quality (Duncan and Magnusson, 2013) and it is expected they would also improve educational, social, and health outcomes.

Evidence Gaps

Additional research and evaluation are needed in these areas, to fill existing gaps in the evidence base.

How old should children be when they enroll in an ECE program?
What should the teacher to student ratio be to assure program benefits?
What is the minimum program length (in months or years) required to achieve beneficial and long-lasting effects? How many days a week should programs be offered, and for how many hours each day?
What are the core components that should be included in program curricula, and how can they best be adapted for different groups and settings?
What are the independent effects of additional program components, such as recreation, meals, health care, parental supports, and social services?
Why does program effect diminish over time? Are there school, family, or environmental conditions that could be developed to improve the maintenance of early benefits?
What are the costs and benefits of providing students with meals and health care, engaging parents, and offering other services with programs?
What are the monetized benefits of self-regulation and emotional development resulting from early childhood education?
If longitudinal studies of state and local ECE programs were conducted, would they find long term benefits similar to those that have been demonstrated through economic modeling?

Study Characteristics

Standardized achievement was reported for 17 studies of state and district programs, 7 studies of Head Start programs, and 3 studies of model programs.
Fewer studies assessed other academic or social- or health-related outcomes, including rates of high school graduation (7 studies), grade repetition (12 studies), assignment to special education (6 studies), crime (5 studies), self-regulation (4 studies), and emotional development (7 studies).
Seven of the included studies assessed the effects of teacher qualifications, and three assessed the effects of program quality.
State and district programs included in the review only enrolled children in families at or below 110% of the poverty level (or with special needs or challenges such as homelessness). Head Start was similarly restricted to children from families at or below 130% of the poverty level. Model programs also have targeted low-income and otherwise challenged families.
Some programs provided health screening, referral, and services for parents.

Publications

Hahn RA, Barnett WS, Knopf JA, et al. Early Childhood Education to Promote Health Equity: A Community Guide Systematic Review. Journal of Public Health Management & Practice. 2016;22(5):E1-8.

Ramon I, Chattopadhyay SK, Barnett WS, Hahn RA, Community Preventive Services Task Force. Early childhood education to promote health equity: a Community Guide economic review. Journal of Public Health Management and Practice. 2018;24(1):e8–15.

Community Preventive Services Task Force. Recommendation for Center-Based Early Childhood Education to Promote Health Equity. Journal of Public Health Management & Practice. 2016;22(5):E9-10.

Hahn RA, Chattopadhyay SK. Linking studies to assess the life expectancy associated with eighth grade school achievement. Preventive Medicine Reports. 2019;16(100980). doi:https://doi.org/10.1016/j.pmedr.2019.100980.

Supporting Materials

Analytic Framework

Analytic Framework pdf icon [PDF - 277 kB]

Summary Evidence Table

Summary Evidence Table - Effectiveness Review - Not available because the CPSTF finding is based on an existing systematic review (Kay & Pennucci, 2014).

Summary Economic Evidence Table

Summary Evidence Table - Economic Review pdf icon [PDF - 132 kB]

Included Studies

The number of studies and publications do not always correspond (e.g., a publication may include several studies or one study may be explained in several publications).

Abbott-Shim M, Lambert R, McCarty F. A comparison of school readiness outcomes for children randomly assigned to a Head Start program and the program's wait list. Journal of Education for Students Placed at Risk 2003;8(2):191-214.

Andrews RJ, Jargowsky PA, Kuhne K. The effects of Texas's targeted pre-kindergarten program on academic performance. Cambridge (MA): National Bureau of Economic Research; 2012.

Apps P, Mendolia S, Walker I. The impact of pre-school on adolescents' outcomes: Evidence from a recent English cohort. Economics of Education Review 2013;37:183-99.

Aughinbaugh A. Does Head Start yield long-term benefits? Journal of Human Resources 2001;36(4):641-65.

Barnett WS, Masse LN. Comparative benefit-cost analysis of the Abecedarian program and its policy implications. Economics of Education Review 2007;26(1):113-25.

Barnett WS, Frede EC, Mobasher H, Mohr P. The efficacy of public preschool programs and the relationship of program quality to efficacy. Educational Evaluation and Policy Analysis 1988;10(1), 37–49.

Barnett WS, Jung K, Youn M, Frede EC. Abbott preschool program longitudinal effects study: Fifth grade follow-up. New Brunswick (NJ): National Institute for Early Education Research; 2013.

Barnow BS, Cain GG. A reanalysis of the effect of Head Start on cognitive development: Methodology and empirical findings. Journal of Human Resources 1977;12(2):177-97.

Burchinal MR, Lee M, Ramey C. Type of day-care and preschool intellectual development in disadvantaged children. Child Development 1989;60(1):128-37.

Campbell FA, Pungello EP, Burchinal M, Kainz K, Pan Y, Wasik BH, Barbarin OA, Sparling JJ, Ramey CT. Adult outcomes as a function of an early childhood educational program: An Abecedarian Project follow-up. Developmental Psychology 2012;48(4):1033-43.

Campbell FA, Pungello EP, Miller-Johnson S, Burchinal M, Ramey CT. The development of cognitive and academic abilities: Growth curves from an early childhood educational experiment. Developmental Psychology 2001;37(2):231-42.

Campbell FA, Ramey CT, Pungello EP, Sparling J, Miller-Johnson S. Early childhood education: Young adult outcomes from the Abecedarian project. Applied Developmental Science 2002;6(1), 42-57.

Currie J, Thomas D. Does Head Start make a difference? The American Economic Review 1995;85(3):341-64.

Currie J, Thomas D. Does Head Start help Hispanic children? Journal of Public Economics 1999; 74(2):235-62.

Deming D. Early childhood intervention and life-cycle skill development: Evidence from Head Start. American Economic Journal: Applied Economics 2009;1(3):111-34.

Deutsch M, Taleporos E, Victor J. A brief synopsis of an initial enrichment program in early childhood. In S. Ryan (Ed.), A report on longitudinal evaluations of preschool programs, Volume 1: Longitudinal evaluations (pp. 49-60). Washington (DC): Office of Child Development, U.S. Department of Health, Education, and Welfare; 1974.

Early DM, Bryant DM, Pianta RC, Clifford RM, Burchinal MR, Ritchie S, Barbarin O. Are teachers' education, major, and credentials related to classroom quality and children's academic gains in pre-kindergarten? Early Childhood Research Quarterly 2006;21(2):174-95.

Early DM, Maxwell KL, Burchinal M, Alva S, Bender RH, Bryant D, Zill N. Teachers' education, classroom quality, and young children's academic skills: Results from seven studies of preschool programs. Child Development 2007;78(2):558-80.

Frede E, Jung K, Barnett SW, Figueras A. The APPLES blossom: Abbott Preschool Program Longitudinal Effects Study (APPLES) preliminary results through 2nd grade. New Brunswick (NJ): Rutgers University, National Institute for Early Education Research; 2009.

Frede E, Jung K, Barnett WS, Lamy CE, Figueras A. The Abbott Preschool Program longitudinal effects study (APPLES): Interim report. New Brunswick (NJ): Rutgers University, National Institute for Early Education Research; 2007.

Garces E, Thomas D, Currie J. Longer-term effects of Head Start. American Economic Review 2002; 92(4):999-1012.

Goodman A, Sianesi B. Early education and children's outcomes: How long do the impacts last? Fiscal Studies 2005;26(4):513-48.

Gormley Jr, WT, Gayer T. Promoting school readiness in Oklahoma: An evaluation of Tulsa's pre-K program. Journal of Human Resources 2005;40(3):533-58.

Gormley Jr, WT, Gayer T, Phillips D, Dawson B. The effects of universal pre-k on cognitive development. Developmental Psychology 2005;41(6):872-84.

Gormley Jr, WT, Phillips D, Gayer T. Preschool programs can boost school readiness [Supplemental material]. Science 2008;320:1723-4. doi: 10.1126/science.1156019.

Gormley Jr, WT, Phillips D, Newmark K, Welti K, Adelstein S. Social-emotional effects of early childhood education programs in Tulsa. Child Development 2011;82(6):2095-109.

Heckman JJ, Pinto R, Shaikh AM, Yavitz A. Inference with imperfect randomization: The case of the Perry Preschool program (Working Paper No. 16935). Cambridge (MA): National Bureau of Economic Research; 2011.

Herzog E, Newcomb CH, Cisin IH. Double deprivation: The less they have, the less they learn. In S. Ryan (Ed.), A report on longitudinal evaluations of preschool programs, Volume 1: Longitudinal evaluations (pp. 69-94). Washington (DC): Office of Child Development, U.S. Department of Health, Education, and Welfare; 1974.

Howes C, Burchinal M, Pianta R, Bryant D, Early D, Clifford R, Barbarin O. Ready to learn? Children's pre-academic achievement in pre-Kindergarten programs. Early Childhood Research Quarterly 2008;23(1):27-50.

Hustedt JT, Barnett WS, Jung K. Longitudinal effects of the Arkansas Better Chance program: Findings from kindergarten and first grade. New Brunswick, NJ: Rutgers University, National Institute for Early Education Research; 2008.

Hustedt JT, Barnett WS, Jung K, Thomas J. The effects of the Arkansas Better Chance program on young children's school readiness. New Brunswick (NJ): Rutgers University, National Institute for Early Education Research; 2007.

Hustedt JT, Barnett WS, Jung K, Figueras-Daniel A. Continued impacts of New Mexico pre-k on children's readiness for kindergarten: Results from the third year of implementation. New Brunswick (NJ): Rutgers University, National Institute for Early Education Research; 2009.

Huston A, Gupta A, Schexnayder D. Study of early education in Texas: The relationship of pre-K attendance to 3rd grade test results. Austin (TX): University of Texas; 2012.

Jung K, Barnett WS, Hustedt JT, Francis J. Longitudinal effects of the Arkansas Better Chance program: Findings from first grade through fourth grade. New Brunswick (NJ): Rutgers University, National Institute for Early Education Research; 2013.

Karnes MB, Shwedel AM, Williams MB. A comparison of five approaches for educating young children from low-income homes. In The Consortium for Longitudinal Studies (Contributors), As the twig is bent . . .: Lasting effects of preschool (pp. 133-169). Hillsdale (NJ): Lawrence Erlbaum Associates, Inc.; 1983.

Keys TD, Farkas G, Burchinal MR, Duncan GJ, Vandell DL, Li W, Ruzek EA, Howes C. Preschool center quality and school readiness: Quality effects and variation by demographic and child characteristics. Child Development 2013;84(4):1171-90.

Lee VE, Brooks-Gunn J, Schnur E. Does Head Start work?: A 1-year follow-up comparison of disadvantaged children attending Head Start, no preschool, and other preschool programs. Developmental Psychology 1988;24(2):210-22.

Lee VE, Brooks-Gunn J, Schnur E, Liaw FR. Are Head Start effects sustained? A longitudinal follow-up comparison of disadvantaged children attending Head Start, no preschool, and other preschool programs. Child Development 1990;61(2):495-507.

Lipsey MW, Hofer KG, Dong N, Farran DC, Bilbrey C. Evaluation of the Tennessee voluntary prekindergarten program: End of pre-K results from the randomized control trial. Nashville (TN): Vanderbilt University, Peabody Research Institute; 2013.

Loeb S, Bridges M, Bassok D, Fuller B, Rumberger RW. How much is too much? The influence of preschool centers on children's social and cognitive development. Economics of Education Review 2007;26(1):52-66.

Magnuson KA, Ruhm C, Waldfogel J. Does prekindergarten improve school preparation and performance? Economics of Education Review 2007;26(1):33-51.

Magnuson KA, Ruhm C, Waldfogel J. The persistence of preschool effect: Do subsequent classroom experiences matter?. Early Childhood Research Quarterly 2007;22(1):18-38.

Malofeeva E, Daniel-Echols M, Xiang Z. Findings from the Michigan School Readiness Program 6 to 8 follow up study. Ypsilanti (MI): High/Scope Educational Research Foundation; 2007.

Mashburn AJ. Quality of social and physical environments in preschools and children's development of academic, language, and literacy skills. Applied Developmental Science 2008;12(3):113-27.

Mashburn AJ, Pianta RC, Hamre BK, Downer JT, Barbarin OA, et al. Measures of classroom quality in prekindergarten and children's development of academic, language, and social skills. Child Development 2008;79(3):732-49.

Peisner-Feinberg ES, Schaaf JM. Long-term effects of the North Carolina More at Four pre-kindergarten program: Children's reading and math skills at third grade. Chapel Hill (NC): University of North Carolina, FPG Child Development Institute; 2010.

Peisner-Feinberg ES, Schaaf JM. Evaluation of the North Carolina More at Four Pre-Kindergarten Program. Chapel Hill (NC): University of North Carolina, FPG Child Development Institute; 2011.

Puma M, Bell S, Cook R, Heid C, Broene P, et al. Third Grade Follow-Up to the Head Start Impact Study: Final Report (OPRE Report 2012-45). Washington (DC): U.S. Department of Health and Human Services; 2012.

Puma M, Bell S, Cook R, Heid C, Shapiro G, et al. Head Start impact study: Final report. Washington (DC): U.S. Department of Health and Human Services; 2010.

Quay LC, McMurrain MK, Minore DA, Cook L, Steele DC. The longitudinal evaluation of Georgia's prekindergarten program: Results from the third year. Paper presented at the Annual Meeting of the American Educational Research Association, Atlanta (GA); 1996.

Reynolds AJ, Temple JA, White BA, Ou SR, Robertson DL. Age-26 cost-benefit analysis of the child-parent center early education program. Child Development 2011;82(1):379-404.

Reynolds AJ, Temple JA. Quasi-experimental estimates of the effects of a preschool intervention. Evaluation Review 1995;19(4):347-73.

Roy A. Evaluation of the Head Start Program: Additional evidence from the NLSCM79 data (Doctoral dissertation, University at Albany, State University of New York); 2003.

Schweinhart LJ, Barnes HV, Weikart DP. Significant benefits: The High/Scope Perry Preschool Study through age 27. Ypsilanti (MI): High/Scope Press; 1993.

Schweinhart LJ, Montie J, Xiang Z, Barnett WS, Belfield CR, Nores M. Lifetime effects: The High/Scope Perry preschool study through age 40. Ypsilanti (MI): High/Scope Press; 2005.

Schweinhart L, Xiang Z, Daniel-Echols M, Browning K, Wakabayashi T. Michigan Great Start Readiness Program evaluation 2012: High school graduation and retention findings. Ypsilanti (MI): High/Scope Educational Research Foundation; 2012.

Sontag M, Sella AP, Thorndike RL. The effect of Head Start training on the cognitive growth of disadvantaged children. Journal of Educational Research 1969;62(9):387-9.

Vance BJ. The effect of preschool group experience on various language and social skills in disadvantaged children: Final Report. Stanford (CA): Stanford University; 1967.

Wasik BH, Ramey CT, Bryant DM, Sparling JJ. A longitudinal study of two early intervention strategies: Project CARE. Child Development 1990;61(6):1682-896.

Weiland C, Yoshikawa H. Impacts of a prekindergarten program on children' mathematics, language, literacy, executive function, and emotional skills. Child Development 2013;84(6):2112-130.

Wong VC, Cook TD, Barnett WS, Jung K. An effectiveness-based evaluation of five state pre-kindergarten programs. Journal of Policy Analysis and Management 2008;27(1):122-54.

Xiang Z, Schweinhart LJ. Effects five years later: The Michigan School Readiness Program evaluation through age 10. Ypsilanti (MI): High/Scope Educational Research Foundation; 2002.

Zhai F, Brooks-Gunn J, Waldfogel J. Head start and urban children's school readiness: A birth cohort study in 18 cities. Developmental Psychology 2011;47(1):134-52.

Zigler E, Abelson WD, Trickett PK, Seitz V. Is an intervention program necessary in order to improve economically disadvantaged children's IQ scores? Child Development 1982;53(2):340-8.

Included Studies - Economic Review

Barnett WS, Masse LN. Comparative benefit-cost analysis of the Abecedarian program and its policy implications. Economics of Education Review 2007;26:113–25.

Bartik TJ, Gormley W, Adelstein S. Earnings benefits of Tulsa's pre-K program for different income groups. Economics of Education Review 2012;31:1143-61.

Cascio EU, Schanzenbach DW. The impacts of expanding access to high-quality preschool education. National Bureau of Economic Research 2013;w19735.

Duncan GJ, Ludwig J, Magnuson K. Child development. In: Targeting Investment in Children: Fighting Poverty When Resources Are Limited. University of Chicago Press (IL);2010:27-58.

Heckman JJ, Moon SH, Pinto R, Savelyev P, Yavitz A. The rate of return to the HighScope Perry Preschool Program. Journal of Public Economics 2010;94:114-28.

Kay N, Pennucci A. Early childhood education for low-income students: a review of the evidence and benefit-cost analysis. (Doc. No. 14-01-2201). Washington State Institute for Public Policy, Olympia (WA);2014.

Reynolds AJ, Temple JA, White BAB, Ou SR, Robertson DL. Age 26 cost–benefit analysis of the child-parent center early education program. Child Development 2011;82:379–404. doi: 10.1111/j.1467-8624.2010.01563.x

The White House. The Economics of Early Childhood Investments. Executive Office of the President of the United States, Washington (DC): 2014.

Washington State Institute for Public Policy (Extended work).National estimates for state and district and federal Head Start early childhood education programs. Author (WA): 2015.

Additional Materials

CDC’s High-Impact in 5 years External Web Site Icon initiative recommends early childhood education based on evidence it improves cognitive and emotional development, self-regulation, and academic achievement within five years and has economic value.

Search Strategies

Search Strategy – See: Kay & Pennucci, 2014.

Review References

Campbell FA, Ramey CT, Pungello EP, Sparling J, Miller-Johnson S. Early childhood education: Young adult outcomes from the Abecedarian project. Applied Developmental Science 2002;6(1):42-57.

Duncan GJ, Magnuson K. Investing in preschool programs. Journal of Economic Perspectives 2013;27:109-31.

Kay N, Pennucci A. Early childhood education for low-income students: A review of the evidence and benefit-cost analysis (Doc. No. 14-01-2201). Olympia (WA): Washington State Institute for Public Policy; 2014. Available at URL: http://www.wsipp.wa.gov/ReportFile/1547/Wsipp_Early-Childhood-Education-for-Low-Income-Students-A-Review-of-the-Evidence-and-Benefit-Cost-Analysis_Full-Report.pdf.