I agree entirely. Childhood is where children learn to be adults. Putting them in a fake environment away from real adult humans denies them the chance to adapt to the real world.
However, Puttnam seems to be hung up on something to do with computer games. I'm much more concerned about schools.
Rather than inflict my own clumsy prose on you all, here's Paul Graham:
If I could go back and give my thirteen year old self some advice, the main thing I'd tell him would be to stick his head up and look around. I didn't really grasp it at the time, but the whole world we lived in was as fake as a Twinkie. Not just school, but the entire town. Why do people move to suburbia? To have kids! So no wonder it seemed boring and sterile. The whole place was a giant nursery, an artificial town created explicitly for the purpose of breeding children.
Where I grew up, it felt as if there was nowhere to go, and nothing to do. This was no accident. Suburbs are deliberately designed to exclude the outside world, because it contains things that could endanger children.
And as for the schools, they were just holding pens within this fake world. Officially the purpose of schools is to teach kids. In fact their primary purpose is to keep kids locked up in one place for a big chunk of the day so adults can get things done. And I have no problem with this: in a specialized industrial society, it would be a disaster to have kids running around loose.
What bothers me is not that the kids are kept in prisons, but that (a) they aren't told about it, and (b) the prisons are run mostly by the inmates. Kids are sent off to spend six years memorizing meaningless facts in a world ruled by a caste of giants who run after an oblong brown ball, as if this were the most natural thing in the world. And if they balk at this surreal cocktail, they're called misfits.
Read the whole thing. I want to rant on about this, but there isn't a single thing I can say that Graham doesn't say better.
See also Robert Epstein's book, which I haven't read, but I listened to this podcast with Epstein from the Glenn & Helen show.