How would children in Colorado, North Dakota or California have differing requirements for education? Surely all kids should have equal access to quality education?
Relocating your family across county or state lines in order to be in a better school district is not always an option. And if you happen to get offered a fantastic job in a particular city that has a crappy school system, I wouldn't care to have to choose between the perfect job and my kids' education.
Also I've never understood the concept of "parental rights". By bringing another human being into the world you impose responsibilities on yourself; you do not grant yourself rights. It is not your right as a parent to fill your child's head with your own particular ideology; it's your responsibility to ensure they receive the necessary training to get a foothold on life and be able to make informed decisions.
> The problem is that some people don't trust parents as much as they trust the government...
There's a very good reason for that. The government is a gestalt body that draws on the experience of hundreds of millions of people over some 5000+ years of recorded civilization. The average parent draws on what their parents taught them and does whatever the media and the mother's club tell them to do.
Shall we look to the Kansas BoE that removed the requirement for the teaching of evolution? Or perhaps to the teacher that gave detention to a child for handing out copies of Linux and lambasted the distro authors with such vitriol as can only be fuelled by ignorance? What about Fred Phelps? He's just a honest, American dad trying to do the best for his kids and the neighbourhood. So's the guy that named his children Adolf Hitler and Aryan Nation. Josef Fritzl was just another everyman doing the best he could, too.
Of course I've picked a few extreme examples there. I know that the majority of parents are not like that but my point is that people are just people; individually they're prone to strange viewpoints and poor decisions. As a group it can take a while to get a consensus but eventually a result turns up that we can, more or less, all agree upon.
I feel that education is one of those things that should be to a high and national if not global standard. The education system in Australia is generally considered pretty good (I think) but I was truly humbled when I met a French girl who told me about how all high school kids were taught languages, culture and philosophy, not just reading, writing and arithmetic.