I have to say that $500 is a very generous budget! Heck, you could buy like 3 different headphones to do 3 different things (one for school, one for home and one for gaming! lol) ;-)
1) How are you planning on listening to the headphones at school?
Straight from your phone?
2) How are you going to watch movies?
From your Computer? Or from a Blu/DVD connected to a Stereo Receiver?
3) Do you need them to be closed (partial isolation, prevents sound leakage) or open?
I have a bunch of headphones and when I'm playing PC games or watching movies on the PC, I use my $30 trusty Panasonics (on my signature). Trust me, the quality of these headphones are phenomenal and in my opinion rivals a lot of other headphones in the 0 to $100 bracket. Apart from these, again for the purposes of gaming and movie watching ON the PC, I use my Sennheiser HD600s (connected to a Nuforce Icon HDP)
For playing PS3, I usually never use a headset but when I do, I use the PS3 Wireless headphones they released last year. Not the best audio quality ever, but does it job.
For straight up music listening, at work I use the Denon D5000s (they go great with music and movies!), or the Panasonics, or any other portable I have at the moment -- right now the V-MODA V80s!)
At home I use the Sennheiser HD600s or the Shure SRH940s.
Again $500, you can do a whole lot.
In my opinion, I would just tell you to go with the D5000s since they excel with everything I throw at them but they are not really all that portable... nor do they isolate a whole lot.
Not sure if I helped you but if you answer the questions above, hopefully we can narrow down the choices and the community might help you better also.
Thanks and Good Luck!