I think you've over used music in this. For the length of the flash a soundtrack of 3 songs is just a bit much. There is no time to settle in to any of the various moods conjured up. I'm told at every point exactly what my emotional response to a scene is supposed to be and if it wasn't bad enough being ordered around like that, i'm not even capable of following the orders. The changes are just too abrupt.
That said i liked the flash. The animation is simplistic as is the graphical style but you have some neat transitions and some pretty scenes (i especially like how you showed the painting). Some of the scene changes are a little fast and the transitions unsmooth but for the most part i thought the direction/"cinematography" were good.
I also really like how the message is told. It's not an in your face "drugs are bad kids" telling and it has some subtelty. But it doesn't become so subtle that it enters pretension, after a bit of analysis i understand the point you are making, and i appreciate that level of directness.
I don't actually agree with an all round critique of drug use and there are plenty of recreational drugs that can be taken without losing your hobbies/mind. However, i shan't pretend that's a problem with the flash and won't mark you down for it. It's also a school project so perhaps you stuck with a status quo take on drugs to avoid controversy.
I feel i've been a bit negative in this review so let me end by saying that i enjoyed the flash and watched it 4 times. I enjoyed how you told the message and there were some interesting character designs. Keep it up!