The Effect of School Starting Age Policy on Crime

On September 30^th, 2010, then-governor of California Arnold Schwarzenegger signed legislation that would move the birthday cutoff for enrolling children in kindergarten from December 2 to September 1, making the minimum kindergarten starting age five years rather than four and three quarters. The law (SB 1381) brought California in line with many other states that had adopted a September cutoff decades earlier. In order to mitigate the impact of raising the entry age on pupils born between the old and new cutoffs, who would otherwise have to delay entering kindergarten by a year, the legislation established a “transitional kindergarten” to take the place of regular kindergarten for those affected children. 

Raising the school starting age cutoff affects those who delay their entry into kindergarten as well as those who do not.  Those who delay their entry and show up to kindergarten a year older are likely to be more mature and ready to learn than their younger counterparts, and are likely to have something of a head start on vocabulary, reading, and following directions.  This is often the reason why parents choose voluntarily to “redshirt” their children. For some children, though, the redshirt year is probably not as productive as being in school; this will depend on what alternate activities are available. Thus, the net impact of delayed entry on achievement is ambiguous.

There may also be spillovers on children who were not directly affected by the laws. Raising the minimum entry age increases the average age within each grade. A class that is older on average may learn more than one which is younger due to positive peer effects and fewer behavioral disruptions. This effect may be substantial given that the benefits accrue over one’s entire career in elementary and secondary school.

In this study, I look at whether school starting age policy affects the likelihood an individual is incarcerated as a teenager or young adult. The study adds to a growing literature that examines the extent to which education policy can be used to reduce crime. Recent evidence suggests that peer effects, and in particular the age composition of one’s peers, has an important effect on criminal involvement. Since school starting age policy directly and exogenously affects the age composition of one’s peers, this makes crime a potentially interesting outcome to study.

To investigate the impact of school starting age laws on crime, I compare incarceration rates among individuals who reached formal schooling before and after changes to the laws, while controlling for a number of observable characteristics in a difference-in-differences regression framework. This comparison is made both among individuals directly affected by the laws (i.e., those who were born between the old and new cutoff dates), and those who were only indirectly affected (by, for example, classroom composition effects). Data for the study come from the 1970 and 1980 U.S. Census, covering individuals born between 1940 and 1962, and including information on incarceration status, state and year of birth (to assign school starting age), and some limited demographic and education information. 

I find that incarceration rates fall among both directly and indirectly affected individuals. A one-month increase in the minimum school starting age is associated with a 10 percent reduction in crime among directly affected individuals, and a 13 percent reduction among the indirectly affected. Thus, overall, both groups benefited from a higher school starting age. But the gap in the reduction implies that those who delayed their school entry were harmed by the delay itself (i.e., the reduction in incarceration was smaller than it otherwise would have been). This finding is consistent with children learning less in their redshirt year compared to those enrolling on time, experiencing less within-grade learning throughout school, or with late entry crowding out final educational attainment.  

The paper provides further evidence that early childhood education programs can yield benefits much later in life. The results suggest that California policymakers were prudent in establishing transitional kindergarten in order to provide instruction for children who would otherwise be outside the formal schooling sector. That being said, we should be cautious about generalizing the results of the paper, at least as they apply to those who delayed kindergarten entry. Current cohorts of children have access to a number of pre-kindergarten programs (like Head Start) that were not available back in the 1940s and ‘50s, and these alternative programs might mitigate any adverse impact of delayed entry into kindergarten.

The full study can be found in John M. McAdams, “The effect of school starting age policy on crime: Evidence from U.S. microdata,” Economics of Education Review, forthcoming.