Hello.
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!