It really comes down to costs and efficiency. Having large enough class size and thus grade level makes things more efficient. As teachers do scale to certain number of pupils. Current schools can teach same material for say 15-40 students at one time. But in more tutoring like system you might be able to do 5. Which means you need 3-8 times more teachers.
I don't think it does. I think it comes down to legal frameworks that inhibit major changes to education systems.
There are methods that you could use to increase mentorship and attention by distributing expertise to less-credentialed individuals. This is done in many other credentialed institutions, like hospitals, colleges, or universities.
Beyond that, you could utilize technology in blended learning. This lessens a load on a teacher.
From what I understand, much of this cannot happen easily because there is a gigantic top-down system distributing rules to institutions. On top of that you have labor agreements that blend into those rules and so on.
It seems accomplishing major reform, outside of curricula alone, would be a massive undertaking.
