Ah, I've been having the same problem with cards getting taken away. One thing I can think of is finding a way to make the deck disappear instantly. I believe I've seen a topit like device used for this before, but you might be able to devise a pull for the card box?
I have found that if I do magic during or right after lunch until lunch is over that it is ok. And there is a 15 minute break after 2nd period and if I go outside I can do magic then. If it is good enough the kids will probably follow you out wherever as long as they get to see some. I also have a couple teachers who really like it and let people circle me and waste class while I do magic for the class. But if you're not that lucky, and can find any time to sneak some card tricks in...
I'm thinking:
-Coin Tricks (obviously). I like using some Raven stuff if you have one.
-Sponge Balls
-Really sponge anything...rabbits,cubes, etc...
-Even though its a card, hover card is only one card. This can sometimes cause problems at school depending on your crowd control skills and the grade. For 9th I wouldn't advise it though unless you really want to.
-I see no reason why TT(thumbtip) effects wouldn't work. If at lunch a sugar/salt vanish and reproduction. Pull out a silk for no reason. Hundred Dollar Bill Change.
-I also think you might start looking into psychology(as it helps) and mentalism. Pick up some videos from Banachek and the like, start learning more tricks with the mind. A lot of those don't use anything more complicated that a sticky note and a pen. It packs a big punch if played right, and besides some thinking you are a magician, many will see you as paranormal and psychic...scare the teachers a bit eh? Get back at em?
-Pull out some paper cups and paper balls...do a version of cups and balls.
-Rubber band through pencil if you know it. I forget the name but it's one from Jay Sankey.
-Speaking of which, if you have the money or access pick up a few resources or dvd's on impromptu magic. "Anytime Anywhere" for example. Or Sankey's "No Card Tricks".
Theres some ideas. Just think about it and maybe invent a few of your own with school stuff. Pencils, erasers, chalk? And just have fun with it....who needs cards anywho?
-- but anyway, he walks up, says "do you do magic?" I said "yeah" and he goes "you're really talented now put the cards away." 
