This story has a lot of valuable lessons to be learned. The first lesson, I think, that you can take from your experience is that you are wholly unqualified to deal with the political and management issues involved. Therefore, do not involve yourself in management or politics. The (non-technical) suggestions given have all involved either an upward appeal to authority, or coercive measures. These will only make matters worse for you. If you want to keep your job, and think that you actually have a chance to make things work, ingratiate yourself to some people who can support you if things go south. I doubt very much that you are being deliberately set up as a fall guy. The school, after all, has a need to stay somewhat technologically relevant, but they're doing it on increasingly less money.
I'm guessing you went into education because you want to make a difference. Some people I know did as well, and they all tell the same story. Long, hard hours with very little acknowledgement. I would guess that's a reality of education these days. With a budget that's always short on funds, management will squeeze every last drop of effort from every employee. So, work under the assumption that the people who hold the purse strings are under at least as much pressure as you are. Maybe it's not true, but there's nothing you can do about it except quit.
Off the top of my head, the best people to get on your side are teachers and students. While you can't solve everything all at once, perhaps there are some small problems you can solve for specific people. And, while someone joked about making network maintenance an elective, there's probably some truth to it. I volunteered to help out the sole network admin when I was in high school. Perhaps some bright students would be willing to help out in exchange for some tutoring. The important thing is that some people know who you are and what you do, and can commiserate since your job is just as difficult as theirs. If it's important to you, hang in there. If it's not, then it's probably time to look for something less stressful.