The good news for Harry Elgood is that he lost more than a stone during his month in a 1950s school.

The 16-year-old public schoolboy found rigorous physical education lessons and the post-war diet of Spam fritters and tapioca proved excellent for weight-loss.

The bad news was his exam results. In the same week that Harry received A* and A grades for eight GCSEs he discovered he had failed all four of his O-levels.

His results were revealed in this week’s final episode of Channel 4‘s That’ll Teach’Em, a reality television experiment in which 30 pupils were placed in a mock-up boarding school.

Harry, who attends the pound;19,000-a-year Radley independent school, told The TES he did not want to make excuses for his poor results.

But he pointed out that he was a dyslexic who usually received extra time in tests and leniency for spelling mistakes. Unfortunately his condition was generally unrecognised five decades ago.

“I told Dr Pidoux, the English teacher, that I was dyslexic before the exams,” Harry said. “All she said was, ‘What’s a dyslexic?’”

By the end of the series, one pupil had been expelled from the fictional King’s School and another left for dietary reasons. The remaining 28 sat shortened O-levels in English language, literature, maths and history.

Only seven - all high-fliers at GCSE - passed all four O-levels. Most passed at least two, while five students, including Harry, failed every one.

The results sparked predictable headlines claiming that education standards had fallen. But the teenagers who took part are convinced that 1950s pupils would have fared poorly if they had been transported to the present day and given three-and-a-half weeks to put on a Shakespeare play and sit GCSEs.

“I’d like to see them using a scientific calculator,” said Kathryn McGeough, a student at Torquay girls grammar.

Kathryn passed three O-levels but failed the maths exam despite succeeding in the mock paper.

She was surprised by how much she had enjoyed the girls’ lessons in deportment.

“People notice that I stand differently now,” she said. “I thought the lessons were a bit sexist at first, but now I think that my improved posture will help me in job interviews.

“What I will miss most is the silence. It was nice being able to put your hand up in a quiet classroom rather than having to shout over the noise - you learn more in a short space of time when it’s silent.

“I’ve also found it strange how materialistic everyone seems and just how much stuff there is to buy. I was getting school supplies at a stationery shop and couldn’t believe there were so many different sorts of ring-binder.”

Kathryn and Harry said they wished some of the 1950s strict discipline could be introduced in modern schools. But they were looking forward to more “interactive” AS classes after hours of lectures from teachers at the blackboard.

“We won’t just be vomiting memorised facts on to the page,” Harry said.

Series producer Simon Rockell, who also acted as history teacher, said it was a gross simplification to say the programme showed that O-levels were superior to GCSEs.

“What was really interesting was the spread of O-level results we had,” he said. “It doesn’t mean that O-levels are better, but it suggests we could be doing more to stretch brighter students.”

However, his views were not shared by Simon Warr, the French and classics teacher. His worst suspicions about dumbing-down were confirmed when he discovered many students could not conjugate the verb avoir.

He is relieved to be returning to the modern teaching aids at the private school where he works, Royal Hospital School in Ipswich.

“I teach at a school where there is a strong tradition of discipline, so in many ways it won’t be very different, but I will be able to use videos in lessons and I’ll have a photocopier,” he said.

“I don’t think that I could have gone back to teaching if that meant a comprehensive.”

English teacher Liz Pidoux is looking forward to joking with her pupils at The King’s School, a private school in Canterbury, after weeks without smiling in class.

However, she said her experience had made her less apologetic about teaching old-fashioned lessons on technical skills such as grammar. “I am going to be braver about boring my pupils.”