INDIANAPOLIS (AP) — Indiana Supreme Court justices want to know whether the nation's largest school voucher program primarily benefits students' parents or religious institutions.

The five justices prodded lawyers for both sides on that point Wednesday during a hearing on a constitutional challenge to the 2011 law under which more than 9,000 students have switched from public to private schools with help from state funds.

Supporters say the voucher system allows parents to send their children to private schools they otherwise couldn't afford. They say parents decide which schools receive public voucher money, not the state

But opponents say virtually all the voucher money goes to religious schools, and the system undermines public education. The impact of the Indiana vouchers is being closed watched because they are available to middle class students.