Lengthening time in preschool is good! Or is it?

A new article published in Early Childhood Research Quarterly indicates that receiving an additional year of preschool education benefits disadvantaged children. The authors conducted a study of children participating in a daily preschool program in Harrisburg, Pennsylvania, who were largely from disadvantaged backgrounds. They compared the outcomes of the children who participated for two years (entering at age three) and one year (entering at age four). Assessments were conducted simultaneously across participating schools by a team of research assistants in the fall of each year. The findings showed that receiving a second year of preschool led to significant improvements in the children's early literacy and numeracy skills and school readiness.

However, a new paper by Canadian researchers offers a different perspective. The authors investigated the long-term effects of the length of early childhood education using a variation created by a policy experiment in British Columbia in the late 1980s. The experiment resulted in a period where some children attended kindergarten for only six months, and others for sixteen months (compared to the usual ten months). The students were tracked over time, and of the original sample, 82,499 students were tracked as far as their grade ten (age 16/17) math and reading tests. The authors found that "long kindergarten" reduced grade ten math scores by about 2.6% of a standard deviation, and reading scores by about 6.2% of a standard deviation, though only the latter is statistically significant. The findings also implied that being in kindergarten longer increased the probability of grade repetition. Negative effects were highest for disadvantaged students and males. However, the authors note that the strong negative effect for long kindergarten may also arise from larger class sizes, the relatively lower age for this group, and the fact that they may have spent time in a low-quality kindergarten instead of being at home or in formal daycare. 

Johns Hopkins University 

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