In what regard? That they have no right of privacy? That people around them (teachers, other parents, ...) have no reasonable expectation of not being monitored? Should I now treat every four-year old as a walking covert listening device? That six-year olds cannot be trusted to obey rules and recognize limits? And if the kid is so young it should absolutely not be on it’s own, then parents should be around and there’s no need for a monitoring device.
Once an hour GPS (as I suggested) is not the same as "privacy", and yes if the adults trusted with care of a six year old take them somewhere unexpected for a long time, the parents should be able to find out.
You could claim this is a slippery slope that leads to more kinds of tracking (and this may be true), but I am saying that very limited tracking can be a net positive.