When choosing there should be a "What will this change?" option, which gives you an idea.
It predominantly changes which teacher character you have. That option I mentioned will show you a picture of each, so just choose which one you like the look of more. Art is slightly more exhibitionism themed, whereas physics has a somewhat more romantic feel to it. Each only has 2 scenes so far, so it wouldn't take long to see the other option if you wanted to.
Enjoy! :)