In this Aug. 7, 2012 photo, Phillip Covington, right, talks with his son Giovanni as he works on a mathematics lesson in the library of Todd Academy in Indianapolis. Struggling Indiana public school districts are buying billboard space, airing radio ads and even sending principals door-to-door in an unusual marketing campaign aimed at persuading parents not to move their children to private schools as the nation's largest voucher program doubles in size. (AP Photo/Michael Conroy)