First, I will share a speech given by Astra Taylor at Pomona College about unschooling, liberalism, and the use of public school as a system that provides an opportunity to rise up in socioeconomic status:
As a progressive, or a liberal, I think this speech really speaks to the cognitive dissonance that occurs when one considers withdrawing their own children from a public school, and publicly denouncing the system as a whole. Liberals tend to view public school from the viewpoint of egalitarianism- equal education and equal opportunity for all. A child whose parents are struggling with addiction or other crises on a regular basis and do not provide the child with access to books, parks, or other sources of stimulation and knowledge will have a chance to acquire these at school. Despite my passion for unschooling and my disdain for institutionalized education, I still know that this is true, and that compulsory free school is still very much a necessity for a large part of our population.
The fact remains that unschooling is for the privileged few. You need two parents, one of whom makes a living. Or you need to be able to work from home or be independently wealthy or pair up with another family, etc and so on. If you desperately need your child to go somewhere affordable or free AND be in a learning-conducive (so-to-speak) space, you need to send your kid to public school. Waldorf, Emilia Reggio, Montessori, Sudbury Valley, and democratic or “free” schools are anything but free. Tuition can be as high as $20,000 per year per child, or at the minimum $10,000 per school year for the first child. Obviously, access to the “best” schools and education as far as child development researchers and experts on child psychology are concerned are currently only available for the elite, wealthy, or lucky.
One democratic school (no grades, all ages mixed, no standard curriculum, etc) that is tuition-free (mentioned in the speech above) is Windsor House School in Canada (British Columbia). I believe this type of respectful educational space should be the new compulsory schooling, publicly funded and if not mandatory, at least encouraged, so that those families who cannot provide unschooling at home are funneled into it.
Did I mention that I feel so lucky that in our very rural, small-town boondock area we now have a public Montessori school? Yes, it sucks that there is mandatory state-testing and grades, but still.
Mother of All Things 
I’m a big fan of public school, but I know they are not all equal by any means. Our one requirement when we were house hunting was that it be in a particular school district which is in the top 5 for our state, but most people aren’t in a position to do that.