Yep, take the advantage of your son's learning phase to make some money. That is not educational at all. There is little to no knowledge at all to be learned from solving captchas. Letter/character matching? You can learn nothing from that.
How is it not educational? Let me tell you. At the moment when your kid has learned how to use a computer, his mind should be able to think of some basic logics already. Even small kids can recognize shapes and sizes already. Your kid has already finished the phase when he has to learn to differentiate the characteristics of an object to another.
Seriously, if you want to educate your kids, then educate them properly. Don't educate them by making them solve captchas and low-key abusing their learning phase to earn some pennies.
I understand what you mean here but we are discussing different stage of kids here, you are into the older kid while im into younger stage of kids. So no matter how I explain it, it just wont fit your idea coz you are looking at the more older kid. Education is kinda boring with kids, even at school teachers try to innovate their teaching into making them believe that they are just playing even though they are actually studying. In my point of view, there is no harm innovating things if it benefits both side.
Haha yeah Kids shouldn't be infront of a computer for a long period everyday, that's where time management come in and you as a parent should implement it. And Kids should play with their friends to develop that social aspect of their life too. But I still believe that there is no harm in trying to teach kids to earn satoshi while playing. If they get bored well, it's up to them