If the computer techs at BoulderTeacher's school are as competent and willing to help as they are at my school district...then it will take a while to say the least.
The easier way (while not the best solution), in the short and medium term, may be an ad hoc network.
Also, the suggestion of having firewalls in place implies that the school owns all hardware. In reality, there is a growing number of students who bring their own devices. This is a hot topic in certain Canadian schools as the moment (it relieves the school from buying and maintaining additional hardware). I'm quite surprised Apple's marketing is not more aggressive on selling the idea of AirPlay to classrooms and finding solutions to avoid issues like those. Whatever happened to selling "dreams" as Steve Jobs used to say? The devices are there, but the solutions are not obvious to most users. I can imagine a lot of other teachers have similar problems. Finding a solution that fits all needs is not easy.
Apple, time to speak to your marketing team. They could try to sell both Apple TV and Airport Express to education touting its advantages and ease of use. For now, it seems that the marketing is very generic and not aimed at education.