An even bigger issue is that nearly half of new recruits quit teaching during training or within three years of starting their career. The profession is haemorrhaging freely at both ends of the age scale. Instead of 200,000 replacements, we probably need to sign up more like 400,000.
Mathematics and physical science graduates are in particularly short supply.
Current students find it hard to believe that many years ago pupils used to be advised to apply for science at university only if they were likely to get high A-level grades. Today's sixth formers are of the view that you get can into university science courses with a couple of grade Es in egg-boiling and kite-flying.
Back in the 1970s it was not too difficult for a university department of education to recruit 30 physicists each year as teachers trainees. Since then, A-level entries in maths and sciences have declined steadily, almost every single year. A similar education department today might sign up five or six new physics graduates, three of whom are likely to quit before long.
The sad fact is that teaching itself is still a brilliant career. It is as exciting and satisfying today to help someone grasp something for the first time as it was 30 years ago.
What wrecks teaching is the suffocating penumbra around it: the bureaucracy, accountability and prescription from above; aggravation from badly behaved youngsters; the inspection regime, still punitive, despite reforms; abuse from hostile politicians and press.
I am currently working with some extremely "challenging" - to use the current euphemism - Year 9 pupils. I would not like to have faced them when I first started. The soul needs time to adjust its "couthness" scale to accommodate the lower end.
Politicians talk of tough action on bad behaviour, from the safely distant warmth of the Palace of Westminster. They eagerly join in the berating of professional footballers like Wayne Rooney for swearing at referees, yet these same besuited paragons behave like utter cretins during Prime Minister's question time.
Barely a dozen MPs turn up to discuss children's issues, such as truancy or poor behaviour, yet they pack the chamber to talk about foxhunting. Have I missed something? The most desperate issues in education command no great interest, yet it is standing-room only to discuss a few prats in red costumes chasing after the local chicken gobbler.
Skilful teaching of the disaffected involves a decent curriculum that engages them, rules and discipline to ensure orderliness, and good personal relationships. Teachers have to craft these ingredients, with varying degrees of success, on a daily basis.
Yet instead of allowing teachers to use their professional judgment about matters like the curriculum, more and more has been prescribed from the centre by politicians and policy advisers, with an eye on the electorate rather than the classroom. The shamefully opportunistic way education is used was nowhere better illustrated than in the school dinners fiasco.
People who for years could not have cared less if children consumed chips and deep-fried ratburger sandwiches, washed down with strychnine cola, then proclaimed a lifelong dedication to healthy eating, all due to Jamie Oliver's brilliant television campaign.
The Year 9 students I work with are infuriating. Talk to them on an individual basis and they are in many cases fascinating: engaging and talented, often in unconventional ways.
Stick them into a class, however, and they become a nightmare, sprouting fangs and claws. Bad behaviour of this kind is an insidious form of bullying, for it denies opportunities for those children who want to work.
It also means that yet another teacher will vow to quit at the earliest opportunity.
One solution is to provide schools with additional teachers, used to dealing with disaffection and disorderliness, so they can operate with individuals and small groups. The idea has no chance whatsoever of being properly funded, however, especially when the political climate is driven by expediency and opportunism, as well as by the need to be seen as taking tough, rather than intelligent, action.
So next time you have an unruly class, the obvious thing to do is to call Jamie Oliver, put on silly red jackets, and chase the kids on horseback across a few fields, while munching a healthy carrot. It may make you look an idiot, but just pretend it is an ancient custom that you are prepared to defend with your last breath and huge political interest will be aroused.