Five years ago, I put my friend Nell Butler in touch with Katharine Birbalsingh, Britain’s most outspoken headmistress. I was hoping Nell, who runs a TV production company, would persuade Katharine to let ITV make a documentary about Michaela, the free school she opened in 2014 and which she’s led ever since. I was director of the New Schools Network at the time, a free schools charity, and was convinced there could be no better advertisement for the controversial educational policy.

At the time, Michaela had yet to be inspected by Ofsted and didn’t have any exam results, but knowing Katharine as I do, and having visited the school a few times, I had no doubt it would succeed. Not only is she an inspirational leader, but she’s a passionate adherent of the ‘no excuses’ approach to education, which I believe is the key to raising standards in the state sector, particularly in disadvantaged areas. The idea is to replicate a grammar school-style of education in a comprehensive environment: so houses, uniforms, plenty of competition, strict discipline and a knowledge-based curriculum, but suitable for children of all abilities.

My hope was that she’d let a documentary crew follow the first cohort of Michaela’s students in their final GCSE year, culminating with them finding out their results, which I knew would be brilliant. But Katharine was worried that a documentary-maker who disapproved of her ‘old-fashioned’ attitudes would bend over backwards to make Michaela look bad. The reputation of her school, which she had poured her heart and soul into, might be destroyed before it had a chance to prove itself. She also pointed out that the stakes could not be higher. Michaela was the test bed for people on our side of the education debate, and a skilful hatchet job would do huge damage not just to the school, but to the cause we all believed in.

Katharine gave Nell a firm ‘No’, and several years went by during which Michaela surpassed itself. It got ‘Outstanding’ in all areas in its first Ofsted inspection and 54 per cent of its first set of GCSEs in 2019 were graded 7, 8 or 9 – A*/A in old money – compared with a national average of 22 per cent. Eighteen per cent of all grades were 9s – the highest mark available. Quite an accomplishment, given that it’s located in an old office building in Wembley, one of the most deprived areas in London, and 41 per cent of its first GCSE cohort were ‘disadvantaged’, i.e. they had been eligible for free school meals at some point in the previous six years. This was an achievement on a similar scale to Leicester City winning the Premier League. Michaela had proved the ‘neo-traditionalists’ right.

I forgot all about my documentary idea until last year, when Nell told me it was finally going ahead. She is nothing if not persistent and, having seen the school for herself and realised what a great subject it would make, she had gradually won Katharine’s trust. I was thrilled. I am as convinced now as I was five years ago that if every state-school parent in the country were given a tour of Michaela, 10 per cent would be horrified – ‘Why is this poor child being given a detention for forgetting his rubber?’ – and 90 per cent would think: ‘Why can’t my local school be like that?’

Katharine hosted a premiere for the documentary in a West End cinema last week and it got rave reviews from the veterans of the education wars in the audience, including Michael Gove. There’s plenty of red meat in it for conservatives – the children are shown singing ‘God Save the Queen’ during a school assembly, for instance – but also moments that will touch the heart of even the most po-faced Labour voters, such as the scene in which a black mother living on a council estate breaks down in tears when she discovers her son has got in. She knows this is his best hope of a great education.

But for my money, the most enjoyable bits are when Katharine hits back at her critics. This is a woman who lost her job as an associate head after she spoke at the 2010 Conservative party conference and who spent four years trying to set up a free school, getting knocked back by one council after another. Left-wing activists tried their damnedest to stop Michaela opening in Brent, and for years she has received vile abuse on social media. Yet here she is, resplendent in a succession of dazzling outfits, having been completely vindicated. If only more headteachers had her courage, we’d have the best education system in the world.