Kansas has a similar law. Schools are not allowed to censor only one side of a controversial subject. Michigan has a policy that doesn't specifically say what rights students have, but it sets guidelines for making rules fair. These apply to much more than issues of free speech and association but of course can help protect students in these cases as well. School rules can't be so complicated the average student won't understand them.
Rules have to be related to valid educational purposes.
Rules can't restrict activities that are constitutionally protected. School policies have to tell you what the punishment is for breaking the rules. The punishment can't be more serious than the misconduct, nor harsher than what the school district itself is authorized to do. A copy of the rules and procedures must be made available to all students. Some states, such as Pennsylvania, have department of education regulations that may protect student rights.