Public schools aren’t designed to be bad, Paul Graham notes; they just seem that way:
There is an idea floating around that public schools are deliberately designed to turn out brainless conformists. I don’t believe this. I think public schools are just what you get by default. If you build a giant building out in the suburbs and lock the kids in it during weekdays in the care of a few overworked and mostly uninspired adults, you’ll get brainless conformists. You don’t need to posit a conspiracy.
I think nearly everything that’s wrong in schools can be explained by the lack of any external force pushing them to be good. They don’t compete with one another, except in sports (at which they do become good). Parents, though they may choose where to live based on the quality of the schools, never presume to demand more of a given school. College admissions departments, instead of demanding more of high schools, actively compensate for their flaws; they expect less from students from inferior schools, and this is only fair. Standardized tests are explicitly (though unsuccessfully) designed to be a test of aptitude rather than preparation.
Form follows function. Everything evolves into a shape dictated by the demands placed on it. And no one demands more of schools than that they keep kids off the streets till they’re old enough for college. So that’s what they do. At my school, it was easy not to learn anything, but hard to get out of the building without getting caught.