How young for a half marathon?

Could you? sure.

Should you? probably not the best of ideas...

As an eighth grader you have plenty of running ahead of you and plenty of races of varying length. why worry about going to the half marathon right now? That is a race to do after you are done running in college. It would certainly not be a good idea to incorporate it into training for track. Training for the 1/2 should be quite a bit different to that of base mileage build up for track season. for now, why not look at doing some 10k's? that would be a much more useful race for you.

If my 8th grade son wanted to do a half marathon it would be fine with me -

The odd thing though - is that I wouldn't let him really train for it - that is run 50 miles per week

But if he wanted to go race 13 miles to see how it felt, why not? A big adventure is good for an adolescent boy - to try big things and take chances.

Chances of injury...pretty small. Chance of boost of confidence: quite high.

I'm pretty sure my son ran one in 8th grade after his first cross country season. He'd just started running and probably wasn't doing more than maybe 20 miles a week. He didn't know anything about PR's but was pretty excited to give it a try.

He went out way way too fast, racing some other kid almost from the start, and totally died at about mile 9. Walked mile 9 to mile 12, and ran the last mile as fast as he could. I actually thought he was going to say he hated it, but he thought it was ok - I wouldn't say he loved it - and he ran the same one a few more times through high school with much better results, but never trying to really run it as hard as he could. It his later high school days, it essentially became his long run for the week, at a bit faster pace.

So I'd say go for it if he really wants to do it. From the times quoted, I'd say he or maybe dad is pretty serious about the running thing. I agree that chances of injury are pretty small - most kids this age will slow down or stop if they are really hurting.