Story has been updated. It was because of a teacher who has a hearing problem that causes her to be sensitive to loud noises, and it is only at assemblies. Cheering/clapping is aloud elsewhere.
You put hearing protection on your kids when you go to the range? That is what the article you linked is talking about. Well not ranges specifically but other places with loud noises.
See above.
Then maybe at assemblies, the teacher that has the problem needs to wear hearing protection.