Basically, it's a one-word answer: school.
When children are old enough to go to school, a serious challenge to their health presents itself: sitting still for what seems like forever - tricky enough in itself - combined with some of the worst furniture design they’re ever likely to encounter. ...
Take a look at a group of 5-6 year olds as they play and you’ll notice that for the most part they move with ease and agility. Then watch some 7-8 year olds and you’ll see the beginnings of hunched shoulders, tight necks, and restricted breathing that you can see more fully developed in many adults. I sometimes ask my Alexander Technique students to assemble a collection of photographs of themselves at various ages. It is striking just how often obvious physical deterioration seems to set in just when they first start going to school. [My emphasis]</blockquote>
Nothing is likely to be done about this problem soon, because it is completely off most people's radar. But it just goes to show - people have it in their heads that "education" is an unmitigated good, but a lot of schools do very silly things to children. No one here needs to be told that they try to feed them the cheapest rubbish they can buy. Here is a perhaps equally important problem.
They spend too much of the day sitting, and they're made to sit in unsuitable furniture.