Cato's latest on vouchers

True Private Choice: A Practical Guide to School Choice after

This is currently latest from CATO

it lists the 5 main Supreme Court points for a voucher system:
"The Supreme Court adopted five basic criteria for a program of "true private choice" in Zelman. First, any government program must have a secular purpose to survive Establishment Clause challenge. Second, a school choice program must offer only indirect aid to religious schools. Third, the benefits of a school choice program must be made available to a broad class of beneficiaries. Fourth, a program must not be set up in a way that favors religious options over secular options. Finally, states must ensure that parents have adequate nonreligious educational options."