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.
Are you a parent? Then teaching morality is your job, not the school's. You can't have it both ways. Don't complain about sex ed, saying that's the parent's responsibility, yet say the schools are supposed to take over the parental responsibility of teaching morals.
Teaching morality in schools cannot not agree with all parents. It could at most agree with small, highly dogmatic groups. For example, I bet the Westboro Baptists all agree on the same exact morals. Expand that into general Christianity and you have thousands of sets of morals at least. There was a deadly riot in this country because the Protestants and Catholics couldn't agree on whose version of Christianity should be taught in schools.