I have school everyday as well, and I keep Terra in her crate when I am there. Think into crate training perhaps ? Helps the potty training process.
And yes. He must learn no matter what that he has to go in THAT spot. As I said before, get a puppy pad or fake grass so he'll be able to see the difference in where to pee instead of just constantly going on the same surface; the floor. Its kind of like if you had a backyard, and he goes pee in the house (in this case he's going in the wrong room) and you instantly take him to the backyard (your case, the bathroom) and make sure he goes there and learns he needs to go outside to pee, not inside ! (In ur case again, the bathroom. xD) He should eventually get it, just like normal potty training. Goodluck !