Excerpts from the executive summary:
New Jersey's Abbott Preschool program is of broad national and international interest because the Abbott program provides a model for building a high-quality system of universal pre-K through public-private partnerships that transform the existing system. The program offers high-quality pre-K to all children in 31 New Jersey communities with high levels of poverty and about a quarter of th e state's children. The Abbott Preschool Program Longitudinal Effects Study (APPLES) assesses the impact of this pre-K program on children's learning and development based on a cohort of children who completed their 4-year -old year in 2004-05.
APPLES previously estimated the impacts of Abbott pre-K at kindergarten entry and second grade follow-up. We found substantial impacts on individually administered assessments of language, literacy, and mathematics at both times. In addition, pre-K was found to reduce grade retention. Previous analysis also indicated that APPLES methodology tends to underestimate impacts. Moreover, as pre-K quality continued to rise after 2004-05, even perfect estimates would underestimate the effect of the program in more recent years.
The 4th and 5th grade APPLES follow-up finds that Abbott preschool programs increased achievement in Language Arts and Literacy, Math, and Science. Our estimates indicate that two-years of pre-K beginning at age 3 had larger persistent effects on achievement than did one year of pre-K. The magnitude of the test score gains from one year are equivalent to roughly 10 to 20 percent of the achievement gap between minority and white students. The gains from two years are equivalent to 20 to 40 percent of the achievement gap. These gains are an even larger portion of the typical learning gain that occurs in year.
For futher commentary and related research see:
New Jersey preschool study findings bolster call for expanding early education programs, CLASP, 27 Mar 13
Participation in Michigan pre-kindergarten leads to long-term benefit, CLASP 14 Jun 12