Apple makes a Watch for kids, mid and above teenagers to be exact. It’s called the Apple Watch.
Regarding early/pre, teens there will be differing opinions. IMHO a smartwatch is not for this young age group. Their brains are not developed enough to both use it as intended or make it something that is socially healthy to keep attached to you IMO. For any medical issue pre teens, go with the specialist medical watch. There’s no thought to wearing it. IMO Keep pre teens off smart devices frequently, which means certainly don’t strap one to their wrist 24/7.