There’s vouchers, as mentioned.

And why is it necessary for education to be ‘free’ or universal for that matter?

People are different, doesn’t mean we all need to learn the same exact things in the same exact way to be productive members of society. Not that such a goal is ever realistically achievable.

???

Free universal education was the key to take poor people out of poverty.

How is this even worth discussing?

Do you realize that if that goes away, we won't be in a libertarian paradise, we'll be back to feudalism?

Countless people from bad environments broke through due to free universal education.

I guess you're not aware of the history on this domain or are just privileged and you don't realize it.

Government vouchers for every child that can be used at any education institution whose curriculum includes the government mandated curriculum.

But then people with resources to do so will shop for the best schools meeting this criteria, which hurts people who don't shop.

I would argue that the presence of a market structure would encourage schools to compete and thus drive educational advances that would eventually be used in all schools. In this way even parents who just choose the closest school without looking at the schools testing history or teaching approach are more likely to have better outcomes when competition is stronger.

1. How does the "government mandated curriculum" get enforced?

2. What are the barriers to entry and the fungibility of the educational market? If the educational market isn't truly a free market, then what's the point? More private monopolies and oligopolies without proper oversight?

1.Through standardized testing to ensure the students are actually learning the mandated curriculum. 2. Barries to entry should be low. Maybe teachers must simply be able to pass the standardized tests themselves? I'm not sure what you mean by fungibility here? And I think this system would reduce monopolies in education since schools could choose whatever methods parents preferred, which encourages different approaches. Also the monopolies of the current system, government education departments and religious institutions, would be financially penalized if they underperformed and parents choose alternatives.