Every Friday for two years running our high school flight club has flown the Syma X1. With the Syma we get a complete RC setup including quad copter, battery, charger and transmitter, and we get it all for $29-$33 (find them on Amazon, or check out equivelant quads from Walkera at Xheli).
Most students can fly these right out of the box (when the X1 is set to beginner mode). They'll run into walls and power into the floor, of course, but the Syma can take a real beating. When one finally does break we save it for spare parts.
An interesting new addition to the Syma lineup is the X11. This quad is smaller but it features 6 axis control, so when the right stick is released it auto-levels itself. We've just bought one and the kids love it (many are buying their own for Christmas). In addition to everything the X1 includes, the X11 comes with a very effective prop guard. Right now they run $27 on Amazon. You really can't beat that.
I've found that job one of starting a school RC club is to get students into the air early and often. Once the hook is set they can be lured into more time consuming scratch build projects, setting the stage for lifetime fun and memories.
Grab a fistful of Symas and start your own club!