Slavery is a lack of Liberty.
Slavery is not just being locked in a cage.
Slavery is being coerced to perform according to some 'authority'.
Students are thus enslaved in school.
Lol, so your essentially saying society needs forced education to enforce libertarian ideals, and then you go on to say that compulsory education is slavery? Make a choice man.
No, ! Without some kind of mechanism any population will eventually abandon whatever current ideals. Governments use forced education. Libertarians have this problem they ignore.
Coerced education is Harm - this is unacceptable. Ideals will always change - that is inevitable evolution. What is not acceptable is people evolving to Harm each other.
Certainty is a very tough target. Persuading people to quit wasting life+resources Harming others and begin using those resources for Learning may be good enough for evolution now.
Unless of course your saying we don't have libertarian ideals, and thus we don't force education. I'm waiting to hear your alternative. I'll be disappointed if it's socialism.
Self-governance. (Lifelong) Learning is the only real choice. Anything else requires coercion, which is Harm. Socialism is a word camouflaging confiscation and slavery.
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."
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...