My kid found that the two most “in demand” skills in a chem lab were statistics and math, and programming (the common statistical packages, plus experience working with large datasets).
Advancing in chemistry is fine- agree with everyone else that self study isn’t nearly as helpful as folks think it is. But labs are not handing over the keys to a HS kid. If he’s going to be useful in a lab setting it will be about the math and the programming.
And then practical stuff- which one would assume would be obvious but actually not- closed toe shoes in the lab (no Birkenstocks). No eating anywhere near the lab. No visitors to the lab unless approved in advance. Nobody walks in without safety glasses. Hair tied back (hence all those “man buns” you see on university campuses- not just a fashion statement). Etc.
Advancing in chemistry on your own without the practical knowledge he’ll get in his HS chem labs (how to write a lab report; how to behave in a lab; what are safety procedures) doesn’t seem worth the trouble.