80MB of WAV music... is that really necessary ? at least to show us you could remove this.
Your chances of getting anyone to at least downloading your game will increase dramatically.
Now about the game...
Honestly, the screenshot looks way better than the actual game
the lack of animation, specially on the explosions, is a real turn off.
The enemy movement could have been smoothed a lot, I had the impression the pilots were sneezing constantly while driving that < looking ship.
There are some design flaws that I think you could easily fix, for example there's no visual/audio feedback when you hit enemy ships. They could blink red.
My shots go past thru the flying asteroids. That means they're in the backgound, right ? Wrong, I died when I hit them. Either they should not hurt my ship or they should block my shots.
Anyway for a game "for school" I think it is quite good. But, if you have time you can make it better.
By the way, I tested on windows XP 32, I just replaced lwjgl 2.7.1 libraries.