One of the best libertarian ideas is that coerced schooling is evil.
Libertarians do not replace it with anything.
The One Law replaces this with ''You need to learn. Everything."
I don't know what libertarians you talk to, but generally that is what we replace it with.
Libertarians I have dealt with still regard law as some kind of kitchen recipe book you can just keep adding pages to and that Harm is just an uncomfortable consequence of whatever...