I think that would definitely count as discrimination to expel someone for that? I currently know quite a few sex workers who are in graduate school and some of which are even about their line of work, however those that are open about it are both in fields that it makes sense for them to be more open minded (one in art school pursuing an MFA and one working towards a PhD in Women's Studies). Regardless, without a doubt, to punish a student and scholar for sex work would be extremely unethical, however the social backlash is a very real fear that keeps many people from being open about that.