So did you buy your teenager a nice warm jacket for Christmas then? Well, that was a waste of time.

They don't wear jackets any more. They don't even wear jumpers much. Their aim in life - especially in the middle of winter - seems to be to wear as little as possible.

Look at any school bus queue. All the first years will be standing there in warm coats, scarves, hats and woolly gloves, all wrapped up nice and warm. The second years have abandoned the gloves and scarf. By the third year they stand with their jackets undone, pretending they're not actually wearing them and by the time they get to sixth form, come wind, rain, snow or sleet, they're standing there in shirtsleeves. Mad, the lot of them.

The serious jacket-abandoning comes at about the same time they start drinking, a good clue there for you. Pubs are too hot and crowded and jackets are too easily stuffed behind a bench and forgotten. In any case they need to travel light, to move on quickly.

As for the girls...when you see them strutting their stuff, giggling, clinging to each other in dresses down to their waists and up to their bums, I long for the ghost of my old headmistress. She considered even a rolled back shirt cuff on a hot summer's day to be "a state of undress", so goodness knows what she would make of that lot.

And I bet their mums have bought them warm jackets too.

Mostly I don't fuss about the boys. After all, they're the ones who are going to freeze so it's their problem, not mine, "but don't dare catch a cold" I yell after a retreating jacketless back, "because I'm not traipsing up and downstairs with hot drinks and aspirins..."

They are, actually, remarkably warm blooded, or thick skinned, or something. Anyway before now they've been sledging in shorts and T shirts and survived without a sniffle.

Then in last week's icy spell, weather forecasters said it was going to be minus 17 degrees. By any standards, that is seriously cold. The boys were going out and for once I was a loving, caring, concerned mother. "Wear your jackets!" I bellowed, blocking their way out through the front door. I talked to them about what it's like to be really cold, reminded them they they'd have to stand in a taxi queue, warned them about hypothermia.

They, of course, took not a blind bit of notice.

Senior Son came home at breakfast time, in jeans and shirt, desperately cold and shivering violently. He'd been to the pub in Richmond, then clubbing in Middlesbrough, gone back to spend the night at a friend's house where, as the temperatures plunged, the central heating had packed up. Ooops.

At least he'd had his jacket to keep him warm. Well no actually - he'd left it in the first pub they'd been into in Richmond...

Smaller Son had abandoned his even earlier, at the home of the first friend he'd called for. Hopeless the pair of them, just like most of their generation.

So if your teenager hasn't worn that nice new jacket yet, or the woolly hat, or the gloves and scarf, then if I were you, I'd take them all back and get something warm for yourself instead - and let the daft youngsters be as seriously cool as they like.