I used to be a teacher. Only over-16s, and only A levels; so I’d start the term by suggesting that anybody who didn’t want to be there should quietly leave, no questions asked. If they stayed, then they were volunteers. As I was.

My old union (now ATL) has a survey showing that one in five newly qualified teachers is planning to leave, apparently because of fear of false allegations made by pupils. Last year at their annual conference they had a different reason, the pressure on teachers from Ofsted and league tables, and tried to claim that standards hadn’t risen. Which is tosh, or they wouldn’t be complaining.

It’s a fiendishly demanding job – not the hours (comparable with most professions) or the money (OK, these days), but the sheer responsibility of moulding children, of getting them to do what you want while giving them an exhilarating experience in your classroom. At the end of the week, if you’re not knackered, you haven’t been trying hard enough, and the kids will know it. It’s hardly surprising that many 23-year-olds, barely recovered from the excesses of uni, find themselves surveying a sea of sullen or bored faces and reckon they should be doing something else.

We’re going to need a lot more teachers in the next decade; plans used to be based on a steady 500,000 births a year, but recently it’s been up to 700,000. During the recession new graduates were queuing up for PGCE places, but that won’t happen as the economy recovers. It doesn’t need a maths PhD to work out that a huge expansion of training places is urgently required. But if we are to improve retention, then another tack is needed.

Mature people should have precedence for training, please. People who’ve had children, understand the responsibility, grasp the significance of getting it right and are alive to the thrill of doing exactly that, day by day. Personality should count far more than A grades at A level (the main perquisite for getting on a PGCE course for years now). The selection process must include an interview with an assessment for suitability for this vital job. TeachFirst, the inspirational providers of teachers for inner-city schools, choose their recruits very carefully, then support them with mentors and discussion groups, yet their alumni have only a few weeks’ training before plunging in. They get great results.

(And if you tell me that without high grades, the newly-qualified teachers won’t be able to spell, I’d reply that even with them, many can’t. As for missing apostrophes... don’t get me started).

I loved teaching. Captive audience, who wouldn’t? One of my Business Studies pupils went on to head up McKinsey in London, so I must have done something right. But I did it with only two weeks’ training at Roehampton, itching to get going, irritated with the incomprehensible jargon. Those that can’t teach, they say, teach teachers. But somebody keen has to teach the kids.