In 2002, only 11 public schools in the United States had gender-segregated classrooms. As of December 2009, there were more than 550. The movement is based on the hypothesis that hard-wired differences in the ways that male and female brains develop and function in childhood through adolescence require classrooms in which boys and girls are not only separated by gender, but also taught according to radically different methods. Although Single Sex Public Education (SSPE) programs are now in place at schools in 39 states and the District of Columbia, other parents and students are not in favor of these programs. It is fair to say the supposed benefits of gender-segregated education in public schools claimed by SSPE supporters are unproven. On the other hand, there is no solid evidence that SSPE is harmful to the learning process of either gender, as critics argue. Likewise, research into gender-segregated education in general, let alone the controversial teaching methods promoted by the SSPE movement, has been inconclusive.