Intellectual status of working-class children adopted early into upper-middle-class families

Failure rates observed (13 +/- 6 percent for school failures, 17 +/- 5 percent for scores below 95 on a collective IQ test) were far below those expected from the social class of birth (55 percent, 51 percent) or observed in a control group (56 +/- 8 percent, 49 +/- 9 percent) but close to those expected from the social class of adoption (15 percent, 15 percent).