It would be viewpoint discrimination in violation of First Amendment rights of free speech if other school personnel were permitted to display items of general interest or encouragement on a faculty bulletin board, but religious messages were prohibited. The only exception to his general legal principle would be if the bulletin board were in a location where it was visible to students. However, school officials may declare a bulletin board off-limits for all but school-related items.
Similarly, if there is a place not visible to students where teachers are free to leave reading material to share with others, religious material may not be singled out for prohibition. If other teachers do not want to read religious material, they are free to leave it alone.
—Keeping Christ in America’s Public Schools, Gibbs & Gibbs, 2008