I acknowledge that there are special categories of speech that can be restricted. Like incitement to immediate violence to a crowd. But, general statements like, "I oppose gay marriage." which are labeled hate speech by one side but which is really just expressing an opinion that some people disagree with...that is what the issue is here. If students think that is not protected free speech, then there really is no protected free speech. Everything is subject to the judgement of the State. We have a long history of protecting such "hate speech." Perhaps we should be asking judge/justice nominees if they accept the settled law on this, or if they want to overturn our free speech jurisprudence.
As to elementary schools, I would say that speech is regulatable to prevent disruption of the learning environment. Obviously, there will be problems at the fringes, and I'm willing to discuss them. And, people can take it too far, like prohibiting a kid from saying grace over his meal, which does not disrupt the learning environment. But, I think the general principle is valid.