Northwestern, Univ. Michigan, and Boston U. are my first thoughts. All are tough to get into, particularly for the theatre departments.
OTOH, thinking about your stipulation that the school must prepare you for professional theatre work, Jenna Fischer went to Truman, which isn’t really considered a hotspot for pro-theatre prep, and made her way from there. A lot of days I think it’s not so much about the school, but more about what you’re willing to put into it yourself. The school isn’t going to hand you the career.