Low-income Indiana students who use a voucher to transfer to a private school fall behind in math, according to a study released this week.

The Indiana State Board of Education approved four private schools with a history of low performance and academic failure to accept publicly funded vouchers.

Indiana's private school voucher program is the largest of its kind in the U.S. Whether it's "social justice" or "an assault" on public schools depends on whom you ask.

The Center for Evaluation and Education Policy at Indiana University compared school voucher programs in Indiana, the District of Columbia, Arizona, Louisiana, Ohio and Wisconsin - all places with a similar voucher program.