Funny is my 12yo son wants to LEARN welding. ??? He's so strange like that. He spends 90% of his free time in front of a PS4. But he's very artistic, does spray-paint paintings and such as well as drawing and suddenly wants to go 3D and learn welding. Told him when he is 14-15 we would take a class or two together.
don't delay. There was a dude who was teaching a TIG welding class, more like a session, a few people really out in the Worcester maker space. Nothing too formal, but lots of personal attention. MIG welding is pretty easy and handy. He advertized other classes as well. I think that's a good deal and an informal intro with everything in class supplied.
I think that I got my kid helping with MIG welding before he even shot his AK, i.e. when he was 6. As long as you got good welding helmet to protect eyes and thick gloves, not too many things can go wrong.