That's amazing, I am really happy about the founders getting teenagers as interns. Those are life long memories for them.
I think SV (and maybe modern capitalism) has corrupted the term "intern" to be "an excuse for us to not pay you" without the other benefits experienced by the "intern".
[EDIT] I should clarify that I am a Brit and never heard the term "intern" used outside of my above definition until I started reading US tech news where it seems to be applied to older people as well.