It's not entirely unreasonable to ask that people associated with school children should take random drug tests. It's important to protect children from drug dealers, as far as possible. But the whole point of random drug tests, surely, is to use a little common sense. The folks who chose him to test, and then pressed the issue, clearly had no common sense.
It's really the same with random bag checks in the NYC transportation system. It makes some sense, but not if they absolutely refuse to do elementary profiling (i.e., young males).
P. S. As the article says, people who work for the schools sign an agreement that they may be drug tested. It's annoying, but it's not a constitutional violation. It's just unfortunate that so many officials seem to be idiots in implementing these policies.