...But parents can’t use the program to pay for Bangor Christian. Maine says it will not fund the attendance of schools that provide religious education—a rule aimed at preventing public funds from being used for religious activity. So while Olivia, now 19, attended Bangor Christian from kindergarten through her high school graduation this May, this meant the Carsons paid entirely out of pocket for tuition, which costs $5,700 this school year for students in 6th through 12th grade. ..

(basically the case is about forcing taxpayers to pay for religious instruction in private schools)