Looking for something to do with the kids this half-term holiday? Forget the theme parks: if it is their long-term health you are interested in, you could do a lot worse than to book them in to see a back specialist. That's the advice from the British Chiropractic Association (BCA), which is so concerned about what it sees as a growing epidemic of back pain among children that 130 of its members are offering a free back check to secondary schoolchildren over the half-term.

Stephen Hughes, a member of the BCA who specialises in treating children, says he has back patients as young as eight on his books, and over the past 10 years he has seen a huge increase in the number of teenagers complaining of backache. "It's something I'm seriously worried about," he says.

"The critical issue is that these youngsters are still growing, and they are already experiencing difficulties. The spine is incredibly resilient and usually it can put up with a lot of wear and tear over many years before it starts to actually hurt. When you're getting real pain in a child that means there's already going to be some considerable inflammation - so by the stage you see them it's an established problem.

"The children coming to me typically have a lot of tension through their shoulders. They tend to have rounded shoulders and tend to hold their head forwards and down. Their posture is usually very bad, and the difficulty is that they haven't ever had good habits - it's not like treating a 25-year-old who had good habits as a child, and who can be reminded of them."

You don't need to be top of the class to guess what's behind the problem: predictably enough it comes down to: a) too much time in front of the television and computer, and b) not enough sport. Today's children aren't just sitting badly, they are sitting badly for too long at a stretch - far, far too long, says Hughes. And the reduction in the amount of time spent doing sports compounds that problem. "Children's spines are very supple and even if posture isn't good, a healthy amount of sport will iron out a lot of the problems," he says. "The trouble is, most aren't getting a healthy amount - some do as little as an hour a week of PE at school, and nothing more."

The effects can be severe. Two years ago, Carol Bristow's daughter Leah, now 13, was taking painkillers every couple of days due to a combination of back pain, neckache and headaches. "It was really worrying," says Carol. "Luckily I'd been to Stephen Hughes with one of my other children about a different problem, so I booked her in to see him. He explained how her posture and the long periods she spends in front of the computer are to blame - he's given her lots of advice on taking breaks from the screen, sitting in a more upright position and so on, and she's a lot better now. Occasionally she'll say she's got a twinge of backache, but it's nothing like as bad as it was."

As with all back pain, the effects are chronic as well as acute. Studies have shown that children who report backache are much more likely to suffer it as adults: according to Professor Peter Buckle, of the University of Surrey's Robens centre for health ergonomics in Guildford, as many as 40% of schoolchildren could be affected. He points to a Danish study which showed that 51% of 13- to 16-year-olds had reported lower back pain in the previous year, and to a study in the north-west of England which found 24% of 11 to 14-year-olds had complained of backache in the previous month. The implication - that as a society we could be storing up huge problems for ourselves in the future - is clear.

Ironically, while back problems are taken increasingly seriously in adults there is little evidence that the same is true for youngsters - despite the potential risks for future health. "Most people have risk assessments in their places of work and companies call in specialists to look at how to minimise back strain," says Buckle. "But few schools are taking this kind of advice. Added to which, when schools first started to introduce computers they tended to set them up in laboratories and the equipment was often all wrong - high desks with high stools and so on.

'It's not just computers, either. Think of the way children are taught these days, sitting around tables in small groups. The teacher is at the front and when she wants everyone to look at the board or face her, some of the children are forced to twist round in their seats to look at her - and sometimes they're in that position for some time.

'Then there's the fact that secondary schoolchildren have to carry so much around with them. Many schools have installed lockers to reduce the burden, but then they sometimes fail to give the pupils time between lessons to get to the lockers and use them - they start off with good intentions, but they don't carry them through."

Hughes says that although there is a steadily growing awareness of the problem in schools, nothing like enough is being done - and he believes it won't be until we start to see the severe knock-on effect of growing numbers of adults with back pain that the issue will be properly addressed.

"We're quite clued up now about how working conditions affect people's backs because it affects productivity - and there's the risk of litigation if a company gets it wrong," he says. "But these don't apply in schools - although it's perfectly possible that tomorrow's adult back pain sufferers may look to their days in the classroom and blame them for a lot of their problems."

A few child back-care tips

· Suggest your child takes a break from the computer at least every 20 minutes

· Try to ensure she gets into good habits in her posture - when sitting she should be upright, with her lower back supported (you might want to think about buying a wedge to support the lower back, available from chiropractors)

· Don't let your child sit doing homework for a long stretch without a break

· If she's working a lot at home, consider investing in a suitable child-appropriate desk and chair

· Take notice of your school's policy on PE, and point out the benefits of exercise

· Encourage your child to play sport outside of school

· Look for opportunities for active family pursuits - walking, cycling, swimming etc

· Take up the offer of a free back check by calling the British Chiropractic Association on 0118 9505950