They’re being paid to provide a service - education - not for piece work - if they really think they can get $500/day for babysitting 30 kids at a time, maybe they should quit teaching and open a private babysitting business.....
The other thing is that you aren’t paying *just* for the teacher. You’re paying for the administration, for the janitors, for the counsellors, everyone in the building. That’s all overhead.