The lesson had been going very well until Philip Prentice, the school curriculum adviser, stalked into the room. I was in mid-flow, putting on my most impassioned American voice as I boomed out Willy Loman’s immortal words in Arthur Miller’s Death of a Salesman: "Biff is a lazy bum!"

Prentice twitched, and stared at me with dagger-like eyes. It was clear that he wanted to talk to me immediately. He was holding a sheaf of folders. Uh-oh. My coursework.

He slapped them down on to the desk and hissed in my ear: "What is this? How am I supposed to send this coursework off to the exam board? Can you see me in my office right now?" My heart thumped. Oh no. My GCSE coursework. I had been worrying about that for some time. I knew it was a bit slipshod.

Later, after I had finished teaching my lesson, I shuffled into his office. Prentice was furious. My coursework had been selected to be sent off to the exam board to be moderated; it was below standard and my marking was inaccurate. I glumly accepted that this might be the case.

"I told them what to do to improve their work. But they didn’t listen," I pleaded. This was the truth of the matter, which I hadn’t been willing to admit until now. Prentice had issued worksheets that gave incredibly detailed instructions about how the children should do their coursework. However, I had quietly rebelled and not handed out the worksheets, deciding to set my own, less guided tasks. My pupils’ work was not of the highly polished standard of other classes.

"What are we going to do? It’s too late to get the children to correct all these mistakes now!" Prentice had a policy of re-drafting coursework until it reached a high grade. "Now I’m forced to alter your speaking and listening grades so that your department reaches its required target grades. But from now on, you will have to follow the instructions on my worksheets to the letter."

Prentice’s words really shattered my confidence. I felt I was an appalling teacher for quite a while after that. Ironically, the students’ overall marks turned out to be higher than the ones I had awarded, because Prentice took the executive decision, without consulting me, to improve my classes’ speaking and listening grades and to lower my written coursework grades. The two components – the written and the oral work – were then added together to gain an overall coursework mark. Prentice’s jiggery-pokery ensured that, despite the debacle of my woeful coursework, my department’s marks were good.

The next year, I decided I would have to follow Prentice’s instructions to the letter. I made sure the work the exam board called for was very carefully "checked" and "marked". In order to perfect the coursework, I sat down with the weaker pupils and more or less wrote the correct answers for them. Prentice was overjoyed with the results. "You’re learning," he said with a wink and a smile. "You’re definitely learning, my son."

Yet, although I now basked in the warmth of his approbation, his comments did make me wonder what the students were learning from the whole process. Year after year, they were being presented with worksheets that told them exactly what content to put in the essays, and if their work was not satisfactory the teacher would "mark" their work very carefully. In my view, while issuing the worksheets and model essays was not the crime of the century, the policy of "marking" in such detail amounted to cheating.

If – as has not been proved – Sarah Forsyth, Prince Harry’s former art teacher at Eton, is speaking the truth, then she "helped" Harry in much the same way that I assisted my pupils at my old school. According to one of her tape recordings, he wrote only a sentence of his art coursework. Nevertheless, he did sign a document saying it was all his own work, and the exam board has exonerated him.

Exam boards must know that coursework cheating elsewhere is endemic. In fact, it is so rife that what used to be called "cheating" is no longer cheating.

For years now, exam boards have been giving top marks to countless "cloned" coursework essays. Very little of the coursework is actually the students’ own work – the student has copied much material from either a) the teacher; b) their private tutor; c) their parents; or d) the internet. Increasingly, the internet is becoming the preferred option for the cautious cheat: for less than £50 a student can have an essay written by an undergraduate.

This is a blight upon education. Coursework was instituted to get students thinking and researching topics for themselves but, in a world where teachers are given pay rises for getting good results, the reverse has happened. All students learn now by completing coursework is that it is a very good idea to imitate exactly what the teacher says, to re-word his words in a plausible fashion, or to get an expert to do it for them.

Now I am a head of department, I have decided to get round this problem by opting for a GCSE course that offers exams instead of coursework. I have also instituted strict rules about the drafting of coursework for A-level: one marked rough draft and then the final version, and that’s it. No endless rewrites.

The proposals outlined last week by Mike Tomlinson for his diploma will not get students thinking for themselves. The final report of his working group into 14-19 reforms is suggesting that much coursework could be replaced by one long project, carried out independently by the student.

However, I feel his emphasis upon teacher assessment will lead to mass fraud, because there is such intense pressure upon teachers to get amazing results. While I am not in favour of lots of exams, I do feel there should be a number of standardised, externally examined tests that measure pupils’ abilities.

I nearly always teach better when I am preparing students for an exam, because I don’t know what the questions will be – I have to teach the whole text, not drill kids to write a very specific essay.

I am afraid Tomlinson’s diploma, and in particular his long coursework project, will not encourage our students to become independent learners. The reason I feel confident in this judgment is because of two words that strike fear into the heart of every sixth-form teacher: key skills.

Tomlinson’s proposals are essentially an extension of the key skills project that has been running in schools now for a few years – with disastrous results. Initially set up to improve students’ literacy and numeracy skills, they have turned into a bureaucratic nightmare that neither improves students’ basic skills nor successfully tests them.

There is a long list of criteria that teachers have to assess, and a few exams to take. Tomlinson’s proposals for the assessment of the diploma look worryingly like the key skills assessment procedures: I can already see the endless tick boxes and bits of paper that tell us precisely nothing.

Perhaps most disturbingly, the Tomlinson proposals completely fail what I might term the "Prentice test". Would a manager like Prentice thrive in such a system? You bet he would. He would be handing out endless worksheets for the students’ "independent" learning schedules; he’d be rigging the results; and he’d have all the paperwork in place to prove that his school was fantastic. Would the students have actually learned anything? No.

I feel like going down on my bended knees and begging Tony Blair to throw Tomlinson’s ridiculous proposals in the bin. Don’t be conned by the jargon. I have had to suffer years of people like Tomlinson speaking their educational gobbledygook – has any of it actually improved what pupils know when they leave school? No.

In many cases, instituting schemes such as coursework and key skills has significantly hampered pupils’ progress. Take it from someone who knows. Tomlinson’s proposals may give the country the illusion that children are learning a lot, but it will only be an illusion. Everything will look wonderful on paper, but pupils’ performance will not improve. Teachers and students are currently being scorched badly in this government’s educational frying pan, but instituting Tomlinson will definitely toss us into the fire, where we’ll all be burned to a crisp.

· Some names have been changed. Francis Gilbert’s I’m A Teacher, Get Me Out Of Here is published by Short Books