Separate but equal: More schools are dividing classes by gender: ...The boys and girls at Imagine Southeast Public Charter School are part of a national experiment in public schools: single-sex education. While a debate rages about the potential merits and dangers of separating students during the school day based on gender, two-year-old Imagine is one of at least four publicly funded schools in the District, a smattering of public schools in Maryland and Virginia, and a profusion of public schools across the country.