Videomaker – Learn video production and editing, camera reviews › Forums › Technique › Editing › Live Video “Editor”/Cut for concert › From what you’re describing
From what you’re describing you’ll probably need at least two pieces of equipment: wireless video and audio transmitter/receiver so you can move freely about the school with your camera, and a video switcher so you can switch from one source to another to feed the projector. These will be expensive acquisitions, I suspect.
Alternatively, you might consider building a delay into the proceedings. Could you roam the halls recording to the memory chip in your camera, hand off the chip to a “runner” and reload for additional recording? The “runner” could take the chip to the projector, close down the movie and project your footage. Repeat as often as necessary?
This might not be as smooth as what you would get with wireless video and a Tricaster, but it would be a great deal less expensive.
Or perhaps you can rent the necessary equipment from a rental house? No matter which choice you make, I’d suggest a thorough rehearsal before the event.