No offense to school kids intended, but I would never lock my bike to the kids rack. Being a school teacher, my income to debt situation is stable but leaves little room for surprises. Even if 95% of the kids at my school are great, there is still that 5% of kids who simply haven't matured yet and still do jerky things. Even though the possibility of loss or damage to the bike is low, I still couldn't replace a stolen bike. Vandalism could be another issue. Piss off a kid on a bad day and they may go and do something to the bike, car, classroom, etc.
I will say that it is extremely rare. These types of things have only happened to me maybe once every ten years, but it is incredibly irritating. I would be very upset because events like this would discourage me from bike commuting and I don't want that to happen. It's just not worth it.
And who cares if they kids ask why the teachers get special treatment? They have such an air of entitlement now a days. Yes, teachers and students do get different treatment. They are only there for 4 years. I will be staying around for 40. I'm sorry but there is a bit of a hierarchy there whether they like it or not. Same thing applies to other parts of life. They need to learn to accept that.