What happens when the kid installs a different browser?

Agreed. Which is why I think the OS level is dumb. Kids can just live boot or launch a vm or keylog their parents' account.

If it's windows, they can just live boot into the OS and get access to pretty much all the files anyway, if the parent didn't encrypt things.

My point is, if the implementation is trivial to bypass, why do we need this legislation? Just let the parents use the existing tools we have and parent.