I remember watching "One More Minute" about a year ago and this is definitely a step up as far as animation goes. Don't get me wrong, I really liked that cartoon, but this one shows great improvement in using some great frame by frame techniques and staying close to tweening as well, which is never a bad thing (unless its just a tween that serves no purpose). Anyways, the characters were well drawn out and I love that fact that you didn't decide to use sprites, so extra points for that
As for the story, It was interesting. I may be the only one, but i didn't really understand what was going on. What I grasped was that toad was just showing mario different levels of hell with memorable characters from the game in there. Some people might understand it so I wont take points for that (I understand this is a school project)
I'm impressed that you went out of your way to voice act it. I wouldn't have worked any other way. I didn't particularly like the voice acting (not saying youre bad, but i just didn't work for me). You should probably try to get free voice actors online. They could have done a better job and I know plenty always looking for work.
Overall, good work and I hope to see more later this year