Preschool provides behavioral advantages

Wired - How Preschool Changes the Brain

This article is a short review of a meta-study conducted by researchers at UPenn and Chicago. The study compiled information from other studies on early childhood education and concluded that it is a worthy public investment. One study highlighted by the article showed a long-term reduction in arrests and an increase in high-school graduation rates. The benefits of preschool aren't necessarily related to intelligence: with IQ the boost from preschool can dissipate, (in other cases it lasted, depending on the program). Instead, preschool helped children (and later adults) with more behavioral traits like self-control, persistence, and "grit". These abilities arguably helped students graduate high school and be more capable in society. The economists who did this meta-study concluded that for ever $1 spent in preschool, the public gets or saves $8-9.