“Public schools may, but are not constitutionally compelled to, allow students to opt out of material in classes that is inconsistent with their religious beliefs.”

I’d like to wish that no school allows such bullshit. “Oh, you don’t want to accept the evidence of an ancient earth? Well, that’s OK because it’s part of your religion.” To me that would constitute a dereliction of duty on the part of the school. The point of public school education is to combat ignorance, not to allow it to fester because of the ignorance of some kid’s parents. Making exemptions based on superstitious beliefs only contributes to minting young folks ill prepared to face the modern real world. It also allows groups to segregate themselves by introducing their own superstitious rules; it encourages societal rifts.