Does Title IX specifically exempt single-sex colleges like Wellesley? In 1990 the US Department of Justice sued the Virginia Military Institute for discrimination for not admitting women; does this provision only apply to public institutions, and not private ones?
34 CFR 106.15 covers admissions, and (e) says
Subpart C does not apply to any public institution of undergraduate higher education which traditionally and continually from its establishment has had a policy of admitting only students of one sex.
Subpart C, then, kind of redundantly prohibits "discrimination on the basis of sex in admission and recruitment", so that means there is no prohibition against single-sex public institutions of undergraduate education. The remainder of Title 9 applies, though. "Public" institution does not mean "government-run", it means "open to the public", which Wellesley is, although it is not government-run. I am not positive, but I think DLI is not a public school (even though it is operated by the US Army).