"Because it works for our family."
I think this works for us as a response because it doesn't leave room for 'argument.' How can they argue with that. If I say things about the state of education, then they seize on the opportunity to debate me.
I was just telling a friend yesterday that I'm gonna have busn cards made up that say:
Answers to common homeschooling questions:
1 -- because it works for our family
2 -- we play in multi-age peer groups all the time
3 -- my children are not performing monkeys, please do not quiz them on what they know.