Although it also carries tutorials in arts, computing and science, its core remains secondary school maths, in which it couples hand-holding video instruction with online exercises, from basic addition and multiplication to the farther reaches of algebra and calculus. The success of iTunes U applications from Apple and the rise of the massive open online courses – nicknamed Moocs – at institutions such as Stanford University show the appetite is there.īut the Khan Academy is different. Using the internet to widen access to education is not itself revolutionary. 'It's no exaggeration to say that there's a revolution coming in education, sparked by Sal Khan,' says Rohan Silva, a Downing Street senior adviser on technology. Since 2009, Khan has devoted himself full-time to his Khan Academy, a tutoring, mentoring and testing educational website at that offers its content free to anyone with internet access willing to work through its exercises and pithy videos, the majority narrated by Khan himself. 'I got over the idea that it wasn't my idea and decided to give it a shot.'

'YouTube? YouTube was for cats playing the piano, not serious mathematics,' Khan recalls thinking. The demands got too much – until a friend suggested he could film the tutorials, post them on YouTube and let the family members view them whenever they chose. 'Then the rest of the family heard there was free tutoring,' he says, and more relatives started taking part.

Khan – working as a financial analyst in 2004 after earning degrees from MIT and an MBA from Harvard – started remotely tutoring his cousin, Nadia, in Louisiana, who was struggling with maths. And like a lot of crazy ideas, it started by accident.

Crazy or not, it's an idea that has attracted attention from Downing Street to Washington DC.

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