Flat Earthers and Moon Landing Hoaxers exist. They are free to have those their views, free to believe those views and free to express those views
But if a believer is a teacher, and if he or she starts teaching his or her students that the globes are lies and the moon landing was filmed in a studio the school will put an immediate stop to either the lessons or that person's teaching career
I wouldn't say that the school is censoring that teacher, but instead the school is simply is not permitting non scientific, easily (and often) debunked bullshirt to be told to impressionable school children who may believe it without question