restrictions are necessary within locations that arent voluntary. Schools are not voluntary, schools are under the oversight of the state, the state should dictate the exposures within the facility. This differs from non mandatory locations where people have the authority to move about unrestricted.
Another such issue is ownership, the teacher does not own the classroom, so they dont have authority or freedom to do what they want.
In schools, the distraction factor is the main thing, because unless youre being willfully obtuse, those things are hung up to distract from the core purpose of regurgitating the approved curriculum.
If a teacher wants to hang unauthorized material, they can group homeschool or start a private school, pretty straight forward shit here.
There is a reason why there is such great support for dissolving the education system as it is, we spend the most per pupil with one of the lowest global outcomes. Its because instruction time is on the back burner to all the noise. You think the little yellow guys in asia give a shit about what extra flags they can hang? fuck no, their sole education focus is superiority, and thats why theyre winning globally