I can counter with another question: Where does the First Amendment explicitly mention classrooms? Or is this an exercise of finding such "emanations" as "separation of church and state" and "a woman has a right of privacy that includes abortions". But I won't base my opinion these.
There is no 1st. Amendment right in a public (or private) classroom by reason that a classroom, by definition, is a controlled environment and is a place to learn a subject and not to freely discuss political issues (unless it is a political science class). Furthermore, I find that the contemporary concept that minors have in their possession all of their constitutional rights to be an absurdity. A minors "rights" are vested with that minors parent or guardian until the minor is eighteen years old. Until then, the minor is a protected class and is entitled as such to be clothed, fed, sheltered, medicated appropriately, and educated in such a manner as to be a capable citizen in full possession of their rights when they reach the age of adulthood. The only circumstance that a child would need to be able to exercise certain rights under the Bill of Rights would be if the child had committed a crime.
Now I know that all conservative parents believe that their children have all the rights guaranteed by the constitution, but that concept is a recently modern one and the cause of most of the turmoil in the public schools today. The US Constitution was written for adults, not children. The classroom is not the "public square", but what is taught in this classroom is (or should be) the result of discussions and conclusions by adult participation in the political "public square".
If you think about it, that's really conservative!
"I can counter with another question: Where does the First Amendment explicitly mention classrooms?"
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The First Amendment doesn't mention your home either.
A "controlled environment" as far as necessary for proper order. (i.e. No shouting fire in a crowded movie theater.)
"A minors "rights" are vested with that minors parent or guardian until the minor is eighteen years old. Until then, the minor is a protected class and is entitled as such to be clothed, fed, sheltered, medicated appropriately, and educated in such a manner as to be a capable citizen in full possession of their rights when they reach the age of adulthood."
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Yes minors are a protected class. I am the one doing the protecting; not the government. I provide the clothes, food, shelter, trips to the doctor, and education. I will be the one to determine if they may pray in the school caferteria or carry a Bible to class. Not the government.
If you think about it, that's American.