I expect that, as Cam says, the courts would side with the school district ultimately. The standard they generally impose is not one of efficiency, nor even appropriateness and proportionality, but one of reasonableness. It’s tough to say such devices cannot be considered reasonable, given the school district’s responsibility for the care and safe-keeping of children.
That being said, I find the whole thing to be just another example of schools failing to do what they know works in the teaching (and monitoring and control) of students while preferring a technological solution that, while it does nothing to improve the situation, gives cover to institutions who can them claim to have done something. I mean, what exactly are we to think of, or expect of, a school that cannot seem to keep track of its students and their activities absent electronic tracking means?
We’ve halved the classroom size, while faculty and staff have both grown, and we cannot keep track of students? I think these are the same people who ascribe Johnny’s lack of reading skills to insufficient access to computers. “Educators” are people uniquely qualified in ascertaining the latest politically correct threat to their charges that does not involve actually educating them.