All societies are imperfect. Some have slavery. The idea that there is some kind of "healthy" society that we can achieve if we follow some blueprint( Such as freeing the slaves. isn't so very different from left-wing utopianism, and a slave free nation is utopian, of course and the idea that things the slavery t that you don't like are "cancers" that have to be cut out is positively totalitarian. It's totalitarian to take property away from the slave holders and expect men to be free.
It's possible that some new way will replace existing public schoolsslavery , but there would simply be other things more important than slavery to complain about. It won't lead to some bright new rational world free of slaves .
There are institutions that are soooo evil that they must be abolished, even if those enslaved in those institutions are worse off materially when finally emancipated.
Or look back at Charles Dickens's England. There were reasons why public schooling was adopted and made compulsory. Maybe conditions have changed enought to make a change in education law and policy possible, but it's not going to be the fanatics who make the change.