On paper, Mercia School in the north of England is a forbidding and unfashionable place. Teachers focus unrelentingly on “the acquisition of knowledge”, if its intimidating website is any guide. Lessons are “didactic”, delivered to pupils sitting in orderly rows. Youngsters form lines in the playground before processing silently into class. Failure to bring a pen can earn a demerit. Chatting in the corridors is banned.