Recent changes to Indiana's private school voucher program cost the state about $16 million for the 2013-2014 school year says a report released late Tuesday by the Indiana Department of Education.

The report says the voucher program initially saved the state a little over $4 million a year from 2011 to 2013 until, according to the Associated Press, the state expanded the program and started allowing some students already enrolled in private schools to receive vouchers.

A state education department spokesman told the AP the cost increase "reflects the recent growth in the choice program."

However, voucher supporters are pointing to what they say are flaws in the report's formula for calculating the program's costs.

Vouchers are a contentious issue in the Hoosier state: the program faced and withstood a legal challenge last spring from the Indiana State Teachers Association. The superintendent of schools, Glenda Ritz, was originally one of the plaintiffs but dropped out of the lawsuit once she was elected. Voucher supporters then tried to take the program out from underneath her oversight but eventually gave up on the effort.