In 1999, Illinois enacted its tuition tax credit law, which offers tax credits to taxpayers whose own children are attending school, as opposed to tax credits to businesses and/or individuals who contribute to tuition scholarship programs. Recent data suggest that the Illinois tax credit program is benefiting middle- and upper-class families more than disadvantaged students and families. This paper examines how the Illinois law works, describes the Illinois tax credit debate, and focuses on who benefits and who gets hurt. It concludes that by enacting tuition tax credits, Illinois has severely short-changed its low-income public schools and their students. At a time when the state's tax collections have been severely reduced by the nation's economic slowdown, diverting $61 million (in 2000) through tuition tax credits, with similar or greater costs foreseeable each year thereafter, only adds further strain to Illinois' public schools. Research indicates that this effect is not unique to Illinois, and Illinois' experience reinforces conclusions reached by the People for the American Way Foundation and others that such tax credits primarily benefit wealthier citizens, do not help poor families, and undercut states' abilities to target needed resources to help raise student achievement in less affluent public schools. (Contains 50 endnotes.) (SM)