Children from single-parent homes are likely to score lower in class and on standardized tests than children from two-parent homes, a Johns Hopkins University study indicated. The study is based on the scores of 700 children in first grade and on interviews with the students and their parents, said Karl Alexander, leader of the study. One reason for the results, Alexander suggested, was that single parents' expectations were lower than those in two-parent homes. The study also found black and white students seem to do better with teachers of the other race. Researchers theorized students and teachers extend themselves more with different races.