There will be 12 kids performing on a stage 10 x 8m, 5m high, and due to lack of money we can't afford 12 wireless headsets.
I'd like to hang a couple of condenser microphones off the ceiling and try to pick up as much sound as possible.
What microphones can I use and how high should they be over their heads?

I've got a UB2442FX mixer of Behringer, impendance 2,6 kOhm.

Or does anybody have a better idea?