Thanks to everyone for responding and talking me off the ledge. I was just so stunned, I needed to get it out. I'd known too many people over the years who thought getting some baby chicks was such a cute thing, but then the buggers GREW on them and they didn't know what to do with them (and I'd heard horror stories both at the MSPCA and the museum of science about classroom projects that didn't end well). I imagined the worst. Just the other day, I was visiting the woman I got my last 5 pullets from, and she said that somebody had recently dumped a bunch of roosters in her yard overnight. She'd had to scramble to re-home them, since she already has more than she needs.
Even though I can't take more, I would certainly do everything I could to find people who might take the classroom chickens once they were grown. I've got enough poultry-friendly contacts that somebody ought to know somebody. I'd never just leave them cold like that, knowing I might be able to help.
I agree that watching the chicks' progress into life would be an amazing experience, one that most of those kids would otherwise never have. I will contact the teacher in a nice, friendly way, not a sermon, I swear. Just to see what's going on, and ask if they need help. I may even offer to bring one of my friendlier chickens in to the class for them to see what the end result will be once their chicks have moved on to (hopefully) greener pastures. The teacher may already have long-term plans. I hope so!