These experiments may help explain the “Obama effect” on the test performance of African-Americans. Adult subjects in a study (still unpublished) answered comprehension questions from the verbal sections of the Graduate Record Examinations before and just after the presidential election. The black participants who were tested before the vote performed worse than whites; those tested immediately afterward scored almost as well as whites.

If simple interventions can have big effects, one might assume that bigger interventions would always be even better. But the truth is that some big interventions in education have had only minimal effects. Head Start, which places 3- and 4-year-olds in supposedly enriched classroom settings, and Early Head Start, which works with 1- to 3-year-olds, for example, have been found to have only modest effects on the children’s academic achievement, and these often fade by early elementary school. Likewise, “whole-school interventions,” in which teams of education engineers descend on a school and change its curriculum, introduce new textbooks and train teachers  often at great expense  typically produce little in the way of educational gain.

Some bigger programs have worked well, however. The Perry Preschool, which was set up in Ypsilanti, Mich., in the early 1960s, is a good example. In this school, highly trained and motivated teachers worked with groups of only six black preschoolers in educationally intensive sessions intended to help the severely disadvantaged children develop both cognitively and socially, and the teachers visited the children’s families for 90 minutes every week.

By the time these students reached high school, almost half of them scored above the 10th percentile on the California Achievement Test, compared with only 14 percent of students in a control group. Almost two-thirds of the students who had been in the program graduated from high school, compared with only 43 percent of control students. And by age 27, one-third of the Perry children owned their own home; only 11 percent of the control students did.

James Heckman, a Nobel Prize-winning economist at the University of Chicago, has estimated that for every dollar spent on a prekindergarten like Perry, $8 has been gained in higher incomes for participants and in savings on the costs of extra schooling, crime and welfare.

Similarly, a program called KIPP (for Knowledge Is Power Program) is having remarkable success with poor minority children in middle schools. KIPP students attend school from 7:30 a.m. to 5 p.m., their term is three weeks longer than normal, and every other Saturday they have classes for half a day. The curriculum includes sports, visits to museums and instruction in dance, art, music, theater and photography. During one academic year, the percentage of fifth-graders at KIPP schools in the San Francisco Bay Area who scored at or above the national average on the reading portion of the Stanford Achievement Test rose to 44 percent from 25 percent. And while only 37 percent started the year at or above the national average in math, 65 percent reached that level by spring.

Such creative programs must be tested to ensure that they work as they are meant to. The United States Department of Education’s What Works Clearinghouse, which was established by the Bush administration, has the job of making public all significant evaluations of educational interventions. The Obama administration should heed the Clearinghouse’s reports. Stimulus money should be spent only on programs that work well  and on creating new programs, which in turn should be properly tested for effectiveness.

President Obama is in a position to not only inspire black youngsters by his example, but also make an enormous difference in their schooling  as long as he supports successful educational interventions, from the smallest to the most ambitious.