I identify as a Lutheran and as a Liberal - both of them proudly. I'm also an educator and have seen first-hand the horrors of unregulated homeschooling in Illinois.
When I was teaching full time in a Lutheran school, a girl came to 7th grade who had been homeschooled most of her childhood. She was clearly behind in every subject area, the result of years of half-assed teaching by her parents at home. This is the kind of challenge any teacher is happy to take, and depending on a student's personality this can sometimes turn into a positive situation. Sadly, in this student's case, her natural leadership, independence, and outgoingness clashed explosively with her academic frustration and she made it her mission to cause as much chaos as possible, culminating in a fake sexual-harassment report to the Department of Child and Family Services.
Even worse, as a substitute teacer I met a girl, another seventh grader, who had recently transfered to public school from home. She was illiterate: not "functionally illiterate", but real, peasant-level illiterate. The written word was a complete mystery to her. For years her parents had taken the state tests for her.
Now, not all parents who homeschool their kids are incompetent or dishonest. But some are, and as things are, no system exists to keep the bad ones in line - indeed, the nature of homeschooling almost guarantees that there can't ever be. Parents wanting to protect their kids from public schools, other children... real life... make an incredibly short-sighted decision when they pull them into this very uncertain educational system. It's an unjust decision as well, since obviously the children are in no position to consent to being pulled, even though it is their future that is on the line.