The kid I am thinking of was probably 14, he could have been a pre high school 14 turning 15 yo. Also, he was well over 5 feet and ran in the low 8:40s. This is from memory, which isn't always perfect.
Most of the young phenoms who continued to improve where good at the 800/mile and moved up in distance as they got older. In high school, the longest distance on the track is generally the 2-mile and 5k in cross country. In general, being able to run a fast mile at 13 is a better predictor of natural talent. Running times in long distances at a young age to an extent just means that kid is getting in more volume. I don't have a problem with young kids running long distance, but I don't agree with training for long distance when in high school you are basically going to be a middle distance runner.
Btw, this is not a negative post because a 13 yo running a 33:50 10k is impressive, but I would be more impressed if he ran 4:30 mile for example.