Class vesus Career

I've heard a few people start to talk about interviews for summer internships. Scheduling has already started to be an issue. Can you really tell a potential employer that you are unavailable for an interview because you have class? It's the eternal 'rock vs hard place' --> are we at Rotman to learn (go to class) OR are we here to get a job (go to interview). Regardless, what was already a struggle to manage, time has become even more precious!