The principal effect of professional education of women who are not going to have full working careers is to reduce the contribution of professional schools to the output of professional services. Not that the professional education the women who drop out of the workforce receive is worthless; if it were, such women would not enroll. Whether the benefit these women derive consists of satisfying their intellectual curiosity, reducing marital search costs, obtaining an expected income from part-time work, or obtaining a hedge against divorce or other economic misfortune, it will be on average a smaller benefit than the person (usually a man) whose place she took who would have a full working career would obtain from the same education.Read the whole thing before getting completely steamed at Posner. He's got an elaborate incentive scheme that avoids sex discrimination. The words "raise tuition" jumped out at me.
UPDATE: I think there is strong pressure on law schools to maintain an even balance of male and female students. It is because of this, not worries about full-time motherhood, that new preferences for males are likely to creep into the process.