The contract should work both ways; should parents NOT desire this state of affairs, they should not be sending their children to school. Rather, such parents should educate the children at home, either by themselves, or through private tuition.
I think the point at which the relationship broke down was when schools began to be seen as service providers, with parents as clients and children as objects deposited at the schools by parents for 'servicing' and 'upgrading'. This had at least three bad effects: parents offloaded part of their responsibility, some children no longer thought of teachers as anything but (under)qualified technicians, and some teachers thought of their work as a mechanistic process (no matter how artful).
The only way to repair this situation is to allow the traditional state to persist. Teachers share in the parenting of the child, as far as education goes. You send children to school, the teachers school them. You don't like it, take them out.