The numbers are in on women’s long-term careers in the law—and they aren’t pretty.

More than 50 percent of law school students are women and some 45 percent of associates at law firms, too. But less than 20 percent of those women ever make partner, Roberta Liebenberg, who heads the American Bar Association’s Presidential Initiative on Achieving Long-Term Careers for Women in Law, said Aug. 3 at an ABA panel during its annual meeting in Chicago. Liebenberg is...