I am totally confused how this comment is even relevant. You have literally no basis for it, and it is not even remotely true.
I am basing it on the influence a person's environment has on them. At the workplace or university, a person is more likely to encounter influential peers and mentors.
Telling me a developer is likely to get the same kind of experience working bit jobs as a contractor in high school as they are either doing the same while pursing a CS degree, or working in a development team is preposterous.
Edit: I just realised you're the OP. Add "gaining some maturity" to the things you'll get from the above.
I think he's the kind of young developer that when he moves on to university or the workplace he'll rapidly broaden his skills.