Learning doesn't take place when discipline is absent at school and at home. Public-school discipline has become a basis for lawsuits. At home, discipline is a basis for intervention by case hungry bureaucrats in Social Services and Child Protective Services. Vouchers are a way of seeding orderly private-school classrooms with disorderly students, thus breaking down the education process. If disruptive voucher students of a preferred race or gender were expelled from a private school in order to protect the learning environment, the school, under the current meaning of civil rights, would be subject to discrimination charges.
Private schools work because there is a different culture at work.
Parents provide discipline at home, and parents support discipline at school instead of seeing discipline as a civil-rights violation and an excuse for a lawsuit. Self-selection is also at work. Students in private schools are motivated to learn. It only takes one or two troublemakers to destroy the classroom learning environment. Schooling will improve when public policy ceases to destroy families and lessen control over children.