A slightly different perspective: schools are mass produced education. Mass produced in the sense that they are the lower cost in terms of person hours to produce an educated child. Like all mass produced products, it's better than 1/2 hearted solo attempts to do the same thing, but a parent that can afford to put a huge amount of time into it can do better job as lots of comments here attest.

If true, that also provides an explanation for the rise home schooling: more people can afford to do it.