As intolerant as the sentences you quoted sound, that idea is the mainstay of any internally coherent religion. Devout Christians and Jews, who hold to their Scriptures, also believe and teach that their religion is the only true religion. There is nothing wrong with that. That is why we have the First Amendment, to protect religion from the meddling of government. It is impossible to legislate thoughts, feelings and beliefs, and the free practice of religion is vital to a moral and lasting society. Religion, incidentally, is vital precisely because of its intolerance for deviation from the mores and rules it teaches. It restrains the natural inclination of man toward selfishness and wickedness. We cannot legislate the heart of man…
We can, however, legislate actions. That is the job of government, to protect those rights and liberties for which so many have fought and died these last 200+ years. When hateful beliefs become actions denying others their rights, the government has not only the right, but the responsibility to step in. A group that preaches hate as a core tenet of its religion should be monitored more closely than, say, a group that preaches meditation, because the preaching of hate is more likely to induce violence (thought it certainly does not cause or excuse it, given the free will of mankind).
In summary, the school has a right to teach their religion, and the parents have a right to have their children educated in their chosen religion. When those children become a threat, the government must meet that threat. That is the nature and the price of liberty. And, paid in blood by so many, we should not abandon our heritage now.