A professor at my university tried that, but the students quite quickly made a huge fuss, got the principals office involved, and the universities lawyers informed said professor that what she was doing was illegal, and that she should stop before she got any more trouble. She stopped.
Possibly a poor translation from my side: I'm referring to the "head office" of the university, i.e. the group of people under the direct leadership of the principal, who have the highest administrative authority at the university.