While the SCOTUS has opened the way towards more govt funding of private and parochial schools, at the end of the day these issues must be legislated. I fear that in today's political climate legislation that allowed major cuts in tuition may be impossible.
WHAT ABOUT HYBRID SCHOOLS?
What is a hybrid school? Children attend public school for half of the day, and religious (or ethnic or ethical) schools the other half of the day. Bingo! Tuition is cut by 40% to 50%! Parents of many religious and ethnic backgrounds could be drawn to a hybrid school - and in numbers could effectively lobby for hybrids.
Parents united in seeking hybrid schools would find that many public school administrators would be supportive and would be quite flexible as far as organizing classes for hybrid in general students so that required subjects can be taught in half a day.
Public schools would benefit by having bigger enrollments and therefore more $.
Parents who are concerned about sending their children to public school environments could be accommodated - all the students in a hybrid class would likely come from similar values driven homes. All hybrid families would likely have similar views regarding appropriate behavior.
Day school administrators benefit by not having to compete with public schools.