I've known parents to work their day jobs and then work as school janitors at night for free tuition for their kids at Christian schools. Many Christian schools will work with the parents on a work barter system.
One of my daughter's teachers in Christian school moonlights as the school janitor so that he can send his five daughters through college. His brother works in the area public schools and makes three TIMES as much as he does. A lot of people make these sacrifices!