GAW, you refer to professional courtesy discounts that medical professionals give to one another. These discounts are not common anymore, and in cases where some costs are reimbursed by insurance, these discounts may be illegal. Nevertheless, I do agree that those in chinuch should receive a discount on tuition.
In the community where I lived, anyone in chinuch/ kollel pays no tuition at all. Since their children comprise over one-third of the students in one school, this represented a significant tuition burden for the remaining parents, many of whom earn less that the rebbiem/ kollel members (because this was an “emerging community”, chinuch & kirv professionals were relatively well-paid compared to their in-town counterparts). I understand though that this is not a typical situation.