The high-profile and controversial head of the schools system in Washington DC is to resign at the end of this month. Chancellor Michelle Rhee said questions about her future, since a change of mayor in the city, had become a “distraction”. Her leadership during three years in the post has seen student test scores improved and a deal struck with the teachers’ unions. But Rhee has not managed to turn around a district that is seen as one of the US’s least effective in educational performance.