Unless the kid is covered in full viral PPE, he is not wearing a Covid 19 mask.
The school needs to pass out full viral protection PPE, or just forget about the idea of preventing the spread at school.
Put the kids in a proper respirator used for spray painting pesticide application. Also get a spray bottle of liquid ass from Wall mart.com with instructions to deploy it near the teachers lounge & not to tell any of their friends cause they will blab & be overheard by staff!