As many as 6.3 million U.S. secondary school students - those in grades seven through 12 - are reading below grade level, according to the Alliance for Excellent Education, a Washington, D.C.-based organization that focuses on improving high school graduation rates...When students have gaps in any one of those components, their reading ability suffers, experts say. For example, a student may be able to read fluently but struggle with comprehending what was read, said Rafael Heller, senior policy associate for the Alliance for Excellent Education.