Now children are developing so rapidly that their teaching is not necessary. They just need to provide the conditions and not to interfere. After a while they will be able to teach. The problem is that many parents think that sitting behind a computer is a very harmful and do not allow them to do it.
Isn't it? Sitting in front of a computer doesn't hurt you at all. No pain is given. But, after all these, your kid is being exposed to different things. Even when your kid is just going to facebook, he can still be exposed to porn, weird stuffs, deepweb, and other things that a child shouldn't know about. At times, you will think why does your kid knows about sex when he's too young to have any experience about it. What you don't know is that even the advertisements on some websites porn is involved.
As a kid, I was so addicted to computer. I didn't have that much exercise. Luckily, I didn't get fat but I do have a cousin that shares the same lifestyle and he's morbidly obese. Right from childhood to adulthood, he's just in front of the computer. He secluded himself to other kids and find that the Internet is the right place to socialize. If you don't think that's terrifying, then okay, "sitting in front of the computer is not harmful". Just to you, though.