Keep in mind that for domestic flights you do not actually need ID at all to get past security. The TSA regularly clears people after losing their ID, forgetting their ID, or having it stolen. They pull you aside, ask you a bunch of questions to verify your identity, and let you through if you can answer them. I doubt it will be a problem getting through security with a school ID for a domestic flight, especially if they have a cell phone and a parent on speed dial. The most likely choke point, as mentioned earlier, is interacting with a carrier check-in agent by checking a bag. Carry on, check-in online, skip the counter.