INDIANAPOLIS (AP) – A new study has found that 80 private Indiana schools involved in the state's school voucher program were overpaid nearly $4 million and have returned that money to the state.

The study released Wednesday by the Indiana Non-Public Education Association shows that 80 of the more than 300 private schools participating in Indiana's voucher program were overpaid $3.9 million over three years after making unintentional errors in calculating voucher costs.

INPEA Executive director John Elcesser tells The Indianapolis Star most of that overpaid money was returned by Catholic schools.

Indiana Catholic Conference officials tell the Evansville Courier & Press most errors occurred when schools didn't recognize multi-child and employee discounts before calculating voucher amounts.

A spokesman for state schools chief Glenda Ritz says her office is reviewing the information.