Oh, nobody will kill themselves, but my parents had a big 'ol fashioned gun that would give small hands a second degree burn quick if you grabbed it anywhere even near the business end. We used smaller guns that had lower heat output & flow rate.

Nothing wrong with hot tools, but it's nice to limit the severity of the burns while they're learning. A small soldering iron, for example, will hurt but you probably won't do any serious damage. Similar with hammers, a ball peen or mallet will hurt but won't break skin like a claw could.

When I was a kid first learning about electronics by taking them apart and other general tinkering, my dad usually took a hands-off approach but did look over what I was working on. He stepped in a few times; ie when working on power supplies and making sure the capacitors had discharged or when I was helping change oil that it had cooled down. Using practical examples of learning like these had worked really well for me but was disappointed there was almost no direct interaction with tools until 7th grade in my district. Was also rather surprised that a number of my peers never received even semi-formal training on how to drill or hot glue things together.

When I was a child, probably between the ages of 6 to 8, I liked to make model gliders from balsa wood. My father taught me how to cut the balsa wings and fuselage from a plywood template. Once he's seen me do it a couple of times, away I went with the Stanley knife (not sure what else they're called in other parts of the world. Retractable utility knife perhaps) and was making my own gliders. Not sure why, but this day I happened to be kneeling, rather than working at the bench. Sure enough, the knife slipped and embedded itself in my thigh. Three stitches later, I had learned to be really careful with sharp knives and how to cut things more safely.

I've driven a chisel into my finger while trying to finish a mortise and tenon joint. Use a vice, not your hand, to hold the wood. Came close to ripping out an artery while climbing an aluminium fence, just ended up with a nasty scar on the side of my wrist. I took much more care climbing fences after that. Barbed wire fence scars across my legs though. Can't even remember how that happened.

Anyway, kids do stuff and hopefully they learn without killing themselves. A few cuts, scratches, a bit of blood and some stitches seems like par for the course.

I'm just learning to ride a mountain bike, in my mid-30s. I got 3 stitches in my knee last week. It's apparent my confidence has gone too far beyond my skill level, so time to dial it back a little. :)

At my secondary school, someone put hot glue on the back of someone else's hand, leaving a permanent scar. There's always one idiot.

At my secondary school a girl stabbed my hand with the tip of a pencil (which is still there under the skin).

You don’t need hot glue guns to do damage to each-other.

Why did you hold on to the keepsake?