Quoting khigh:" I wouldn't even do it to my own child. To me, it sets them up for bigger problems when they become ... [snip!] ... If you get indoctrinated in school to think it's okay, there will be no one to fight it if/when it comes down to it later on."
I wouldn't put one on my kid, either. Especially since my kid's school is entirely gated, The doors are locked when the bell rings, and one must go through the office to even get into the main courtyard.
If my kid is there, he's not getting out, most likely. So it's unnecessary. If my kid isn't there, it's not really so much their business where he is, providing I've called the school, whatever. Sure, if he had excessive absences, we'd chat about their concerns, and obviously skipping school would be a big deal to me---but I think I can deal with it without a tracking device.
The ONLY way I'd put a tracker on my kid, is if I were the one doing the tracking, and only if he had been sneaking out at night repeatedly, doing drugs, and all other options had been exhausted.