Abstract: This analysis provided by researchers at the American Federation of Teachers (AFT), the nation's second largest teachers' union, finds that fourth graders in the participating sample of charter schools had lower achievement in grade 4 (six scale points lower in math, seven scale points lower in reading) when compared to students in traditional public schools. The analysis used data from the 2003 National Assessment of Educational Progress (NAEP) which tests a nationally representative sample of students in grades 4, 8 and 12 in a variety of academic subjects.