It hurts to criticise a sparkling teacher. What makes it more painful is that Salman Khan, of the online Khan Academy, is teacher to nearly 35 per cent of the world’s people, that is, those with access to the internet. In The One World School House, Khan writes with “so let me tell you a bit about my background” ease of how a series of YouTube lessons for his cousin Nadia grew into an electronic peepal tree of learning, watered by believers like Bill and Melinda Gates. He also explains his choice of an austere aesthetic for his videos: all you see is a blackboard with a cursor writing in coloured chalk. (Khan is a voice-over.) In later chapters, he outlines what he’d like the academy to become in a world where schooling does not interfere with education. It’s quite a fascinating account, to be sure, although it takes the well-set, well-known pattern of so many celebrated stories of dreamer-doers.