The door of my classroom crashed open as I was explaining the different media techniques used on the front cover of a controversial "election issue" New Statesman. My GCSE class swung their heads around in shock. "Been kicked out again!" shouted Jon. "So I've come to join in your lesson!"

As head of English, part of my job from time to time is to accommodate pupils whom teachers find "educationally challenging". I invited Jon to take a seat. Unfortunately, the political nuances of NS covers quickly bored him and he started engaging in a friendly but loud slanging match with Jenny, another member of the class, which resulted in his throwing bits of rubber at her. Jon ignored me when I pointed out the way one cover was making harsh criticisms of the British government's role in the Iraq war, and said: "What's the use of this crap when I want to be a hairdresser?"

Jon was one of the few in the school who failed GCSE English. His single mother was generally supportive of the school, but ill-equipped to deal with such an abrasive teenager, who bullied and harried her constantly. Jon is exactly the sort of pupil the government is trying to keep in education: a bright, working-class boy from the kind of background that has prevented him from achieving his academic potential.

Since 1997, Labour has introduced a raft of initiatives to solve this problem: literacy and numeracy strategies, work-related learning, new vocational qualifications, key skills, education maintenance allowances for sixth-formers, Every Child Matters legislation, "inclusion" policies, more computers in schools, huge injections of cash into schools in deprived areas, and so on. Have they made any difference? Well, yes and no. The results of pupils from deprived backgrounds have improved a little, but in the vital subjects - English and maths - they remain depressingly low. Fewer than half of 16-year-olds achieve A-C grades in these subjects.

Jon was in that category. None of the government's policies had an impact on him, and that wasn't down to a lack of resources or to poor teaching. The reality is that teachers' hands are tied. In English, maths and science, we have to follow the national curriculum, which virtually dictates what you teach. It is overloaded with content, much of which is too abstract and analytical. So, for example, that lesson using NS covers engaged the articulate middle-class pupils but not the disaffected ones. Freed from the shackles of the national curriculum and its attendant exams, I could have shaped lessons that would have enthused Jon for long enough to make him see the value in writing clearly, correctly and fluently. Only when central government stops being so controlling and puts more trust in teachers will things improve.

I support the new Education Bill, as I believe it aims to do this. Most teachers are fed up with all the changes and are cynical about the government's motives, but I think they will welcome the reform in the long run. This is the first time in decades that a government has realised the importance of giving schools more freedom to adapt lessons to their chosen intake. The bill also encourages parents to become more involved in a school's day-to-day running. In Jon's case, this would have helped immensely. His mother was unemployed; both she and the school would have benefited from her having more to do with the school life Jon was leading.

It will be a great shame if the government's plans are not passed in their entirety. The left wing of the Labour Party wants to give Blair a bloody nose, but it is no time to play politics when the education of future generations is at stake. It's time to encourage clever pupils such as Jon to become more than hairdressers.

Children's names have been changed. Francis Gilbert teaches in an oversubscribed comprehensive in outer London. His latest book, Yob Nation, is published by Portrait in March. Post comments at www.francisgilbert.co.uk