Free speech is not what you think it is. In your scenereo you have the right to try to say what you're trying to say. Just because your opinion is unpopular and people are unwilling to publish (freedom of speech and the press goes both ways, you can't force someone to say something either) does not mean your rights are being infringed. This is universal and not just the US. There are no countries I'm aware of that say "all publishers must publish anything anyone says regardless of their credibility". It would be ludicrous.

And if we go back to my example, that person who believes that they're teaching children something true can go through the proper channels of society to change the curriculum. I'm also unsure if you're actually giving the idea of "black people are out to get you" space or just hypothetically, I chose it as an example that's obviously not true. Replace it with teaching them that strange white vans have candy in them and it's okay to eat it. Or replace it with them explaining to the children sexual actions they desire in great detail. Your absolutism says they should be allowed by the school to do this, and if that doesn't change your mind, I've made my case, you disgust me, and I choose not to engage further.