Instruction in public schools can’t be based on the individual beliefs of students. In math, grammar and most other subjects, there are generally accepted standards of knowledge that should be imparted to students. Two times two equals four; singular subjects take singular verbs in a sentence. Such standards are the basis for education. The same is true in science class. Students can choose not to believe in evolution, but that doesn’t mean they shouldn’t learn about and understand the well-accepted theory on which much of biological study is based.