The way to establish a system that works is to eliminate donation dependency. Schools should not depend on donations to survive and neither should parents.
The problem is not in fixing the percent of income that can be afforded, but in fixing a per child amount. A family with 7 children cannot afford to pay more tuition than a family with 6 children, and that is the problem here. More kids <> more income, ergo, more kids = more scholarship. Every tuition bill requires personal tailoring, and that’s a problem.
Tuition per child needs to be fixed at an amount that is affordable on a per child basis, considering the ability to pay of a high percentage of member families (I made up 75% as a figure). Schools must live with that amount, whatever it is. Families that do not earn enough to pay for all their children will need to do one of two things:
a) Raise their personal shortfall by soliciting tax deductible donations
b) Home school one or more children for all or part of the day so that the final tuition bill is in their means.
I don’t see why 75% of families (or more) have to break their backs to provide to their children something neither they nor their neighbor can afford.
With all the kvetching about money spent on weddings and bar mitzvahs, you would think that someone could think of relating that argument to the school. After all, schools are much larger scale than individuals and should be a more worthwhile endeavor.