Can't speak for any GP/OP but I learned simple welding with 12 when my father built a new grid for the berries in our garden to grow, spot welded a few steel grids together (about 8mm thick). Of course my father watched the first 10 tries or so but after he was sure I would be able to handle it he would go do other things and only occasionally check back to make sure I didn't spontaneously die.