... Are you listening at the back?
He was one of several MPs and celebrities who taught for an hour to promote Teach First, the initiative which speeds high-flying graduates into schools.
When Brett Wigdortz, Teach First's chief executive, said that Jeremy Paxman had been shaking with nerves before his lesson, Mr Balls looked worried.
"Now I know what a rugby player about to go on Strictly Come Dancing must feel like," he said. "I taught first year undergraduate economics at Harvard in 1989, but I'm not sure that has prepared me for this."
He made a confident start with his class of 20 sixth-formers, choosing the familiar topic of how Parliament works.
With his jacket off, he launched into an explanation of the differences between laws and rules.
Mr Balls probably did more of the talking than he had planned: with the Government focus on personalised learning, he should perhaps have let his pupils lead more of the lesson.
However, his class seemed impressed. "It's good to see that politicians have some talents," one girl said as she left the class.
Others taking part in the initiative include Craig Revill-Horwood, the sometimes acerbic Strictly Come Dancing judge.
But the celebrities pale compared to those who visited US schools for a parallel scheme, including Dennis Hopper, Arnold Schwarzenegger, Dr Dre and Oprah Winfrey.
Photograph: Edmond Terakopian.