Had it not been for a handful of exam questions, Alan Jones might been a successful Conservative politician.
In 1948, Mr Jones failed the 11-plus, and was sent to Blackrod school, in Lancashire, his local secondary modern. "I wasn't terribly disappointed," he said. "I was always a hands-on person. I would do things mechanically, rather than using my brain. So I became an electrician."
But now, at the age of 66, Mr Jones has begun to reflect on what might have been. He believes the difference between his career and his unrealised potential is best explained in his choice of daily newspaper: he buys the Daily Mail, but prefers to read The Times. "When I was 22, I was asked to stand as a local councillor. I've always been interested in politics, and I'm a leader. But I didn't have confidence in my education. If I'd gone to a grammar school, I would have had qualifications, and more confidence in the way I speak. It just comes home to you: I wish, I wish, I wish."
Mr Jones is among four secondary-modern pupils interviewed for a BBC documentary, examining selection in schools from the 1940s to the 1960s.
At the Chalk Face uses professional and amateur footage shot at the time, to illustrate the reality behind the division of pupils by ability at 11.
So colour film of Joseph Rowntree, a flagship secondary modern near York, is contrasted with an inspectors' report criticising its standards of English and maths. And footage of grammar-school pupils on a trip to Venice is juxtaposed against images of their secondary-modern counterparts on holiday in Staithes, on the Yorkshire coast.
Richard Taylor, the film's producer, said: "These days, we regard secondary moderns as an educational experiment that failed. But they were launched with worthwhile hopes and ideals, many of which have survived into the education system today."
He is also keen to demonstrate that most secondary-modern teachers took their jobs as seriously as those in grammars. Among the teachers featured in the film is Peter Emmens, whose 38-year career included a starring role in a 1962 BBC documentary filmed at Margaret Tabor secondary modern, in Essex.
Mr Emmens is shown blowing soap bubbles in front of the class, and then asking pupils to write down their reactions: a groundbreaking exercise in an era of English-lesson parsing and recitation. He believed that such innovative practices had as much of a place in secondary moderns as in top grammars and his pupils were so excited by the exercise that not one went to the toilet, during four hours of filming.
"It was a record," the 77-year-old said. "Young bladders aren't famed for their endurance. But we tried to stimulate the desire to write, then develop its mechanics through exercises relating to that. Secondary-modern pupils were lovely and needed our attention. It didn't matter what kind of school it was. We just got on with it."
At the Chalk Face will be shown on BBC4 on January 28 and 29, and on BBC2 on March 7