Marsh said that when Alabama's tax credit program is fully implemented, he expects about $50 million in tax credits every year based on Arizona's similar program. Arizona had about 30,000 student participating and $57 million in tax credits for the 2012-13 school year.
Marsh's $50 million estimate is equal to slightly less than 1 percent of the $5.55 billion the Legislature has appropriated for public education at all levels this year.
The Alabama Association of School Boards uses a $4,000 per-child tax credit to estimate that Alabama's program could cost $30 million if 10 percent of the students in failing schools participate. That figure rises to $300 million if 100 percent participate. But no one expects 100 percent participation in an Alabama program.
Whitney Rhoades, policy director for the school choice organization American Federation for Children, said research on Florida's scholarship program shows parents don't tend to move their children from failing schools if they are doing well. Instead, it's the parents whose children are having trouble, she said.