Proponents of early childhood education looking for backup need only turn to the latest issue of Science magazine.

The survey by James Heckman, an economist at the University of Chicago and University College, Dublin, points to one conclusion: The earlier society tries to help disadvantaged people, the better. Social investments in the preschool years can yield tremendous returns; investments in the early school years can pay for themselves; later investments most likely will not recover their costs.

Specifically, “Early interventions targeted toward disadvantaged children have much higher returns than later interventions such as reduced pupil-teacher ratios, public job training, convict rehabilitation programs, tuition subsidies or expenditures on police.” And, “later schooling and variations in schooling quality have little effect in reducing or widening the gaps that appear before students enter school.”

The Perry Preschool Program in Ypsilanti, Mich., put 3-year-olds and 4-year-olds in school in the morning and had teachers visit homes in the afternoon. By age 10, the children showed no increase in IQ scores compared with those of a control group, yet had better scores on achievement tests. By age 40, they had “higher rates of high school graduation, higher salaries, higher percentages of home ownership, lower rates of receipt of welfare assistance as adults, fewer out-of-wedlock births and fewer arrests.”

Admittedly, it is difficult to duplicate innovative one-of-a-kind programs like Perry, but the author says the rate of return on its investment is 15 percent to 17 percent per year, and the ratio of benefits to cost per child is better than 8-to-1.

This does not mean that all job training programs, or released prisoner re-entry programs and so forth should be junked. But proposed expansions should be viewed skeptically. And well-thought out programs to counter “poor parenting practices and lack of positive cognitive and noncognitive stimulation” ought to be viewed more favorably than, for instance, any proposal for a 141st federal job training scheme.