In zelman v. simmons-harris, the supreme court ruled that a state program providing families with vouchers could be used to

The supreme court ruled that the vouchers could be used to: pay tuition at religious schools.
Initially, the vouchers could only be submitted to publicly owned schools. But the supreme court ruled that private religious schools re also offering similar education like public shools' but only with an additional lesson on Religion. So, both students of these schools have the right to use the vouchers for their tuition.