A long-term study published in the Archives of Pediatrics & Adolescent Medicine and reported in Science Daily examined 19-year-olds whose mothers had been in the Nurse-Family Partnership program in Elmira, NY. Some were in the control (no extra help) group, and others got in-home visits during pregnancy or during pregnancy and infancy. The latter group had about 1/3 as many arrests at age 19 and 1/5 as many convictions as the controls, but only for girls. Boys showed no difference between intervention and controls. The girl difference stayed when they controlled for income.
They did a cost benefit analysis and found that $7000 in program costs returned $9000 in benefits for low-risk girls and $41,000 for high-risk girls (i.e., those with low-income, unmarried mothers) .
Now why would it be that sending someone to help a new mom helps girls avoid jail but not boys? Maybe boys are just worse than girls and become whatever they are regardless of what you try to do. I hope not. Maybe the home nurses paid more attention to girls than boys. I doubt it. Maybe, because girls mature faster, earlier intervention helps girls more. Jeez, I can't even come up with a plausible conjecture.
I'd like to know if the Perry Preschool or Chicago Banks projects or anyone has looked at different long-term effects of child care on boys compared to girls.
God, I love Google. It turns out Perry Preschool did have bigger effects on girls than boys. "Going to preschool nearly doubled a girl's chances of getting a high school degree, but had no effect on boys. ... The preschool had a big effect on whether girls repeated grades or dropped out of school, but it had almost no effect on boys in these areas." Some areas showed effects for boys but always much less than for girls.
If girls benefit more by enrichment than boys, then something in our ordinary way of raising kids is stunting girls' mental development but not boys'.
This has implications for universal preschool or state preschool. If State Preschool (okay, CSPP) helps girls but not boys, it would be more cost-efficient to limit it to girls. Fat chance getting that through the legislature.