Single-sex academies like these two Dallas schools not only benefit the students fortunate enough to attend but also are a part of the solution to the growing boy gap in education and the persistent girl gap in math and science. Today millions of American boys are languishing academically. Boys in all ethnic groups and social classes are far less likely than their sisters to feel connected to school, to earn good grades, or to attend college. Girls, by comparison, are thriving academically, but are still far less likely than boys to enter fields in science and technology. Boys and girls, taken as groups, have different interests, propensities, and needs. These academies can provide important lessons on how to educate our children more effectively.

What sensible person would call these programs and others like them morally and legally suspect? And yet the American Civil Liberties Union says they are. It has launched a major campaign called “Teach Kids, Not Stereotypes” to discredit and terminate gender-specific programs in American schools. For the ACLU, organizing by sex is analogous to organizing by race. Lenora Lapidus, Director of the Women’s Rights Project of the ACLU, seems baffled so few see the connection. “It is, in fact, quite startling,” says Lapidus, “that many people who would never consider segregation based on race or religion in a public school would accept sex segregation.” This campaign is unlikely to advance the cause of social justice. But its potential for mischief is abundant.

No one is suggesting that any student be forced into a single-sex program. Coeducation is an American tradition, and that will never change. But some parents and students prefer girls’ and boys’ schools, so why deny them that choice? What could be wrong with a voluntary program that seems to be doing so much good? Plenty, says the ACLU, and it claims to have research to prove it: a 2011 critique of single-sex education published in the prestigious journal Science.