There will always be somebody there to bitch about something. But we can remove the obvious bias in much of the system. The first order of business is to remove the instruction that is not basic to education. The parts that do try to teach morals go first. It can't be biased if it isn't there. This means no "two mommys" and no Bible verses condemning homosexuality. No "save the planet," no "save our souls." No "utopian paradise," no "socialism sucks." You notice the trend here, in both of the above the liberals do have their point of view in the schools, but the conservatives don't.
Reading, writing, arithmetic, science, the basics. Reading and history are the main places where you have to be careful about bias.
It can’t be biased if it isn’t there.
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Then you are teaching the children to think amorally and godlessly. That isn’t religiously neutral in content or consequences.