Using a new rich source of data, researchers Katherine Magnuson, Christopher Ruhm, and Jane Waldfogel conclude in Does Prekindergarten Improve School Preparation and Performance? (NBER Working Paper No. 10452) that early education does increase reading and mathematics skills at school entry, but it also boosts children’s classroom behavioral problems and reduces their self-control. Further, for most children the positive effects of pre-kindergarten on skills largely dissipate by the spring of first grade, although the negative behavioral effects continue. In the study, the authors take account of many factors affecting a child, including family background and neighborhood characteristics. These factors include race/ethnicity, age, health status at birth, height, weight, and gender, family income related to need, language spoken in the home, and so on.