"They deserve better."
They deserve better than to be taught of the flat-earth of Creationism too. They deserve better than "Because it's written in some oft-revised old book" as a reason for the idea, also.
I am not aware of "flat earth Creationism" being taught or advocated except in a few circles of intractable folks. You're right. Children deserve to be taught the truth and to seek it out. They deserve to know the Theory of Evolution is not above question.