Excerpted from a message board post:
Much about institutional schooling exists not because it's the best or the only way to learn but because it helps with the management issues of a mass-education system. Testing, standardized curriculum, chopping learning up into subject areas and grade levels, homework, science labs, report cards, credits, the top-down model of teacher dispensing learning to student and so on. All this stuff is, in my opinion, part of the school system merely because it makes for a semi-efficient factory model of education. The deeper you get into homeschooling the more you realize that education can really look like anything you want it to. If you're building a single hot rod in your garage you don't need an assembly plant, CEO, union reps, robotic assemblers, ad execs, fiscal planners, lawyers and a mission statement, right?
Same deal with homeschooling.