The blue surgical masks are worthless but that is what most kids end up wearing (because they are cheap). The decent N95 masks do provide some protection if worn properly. The last controlled study I saw on them indicated they provided about 15 minutes of protection when within 3’ of a non mask wearing person. If both persons were wearing N95’s correctly the protection went well above an hour. No standard mask eliminates the virus getting through entirely but what you are trying to do is decrease the viral load you are exposed to and for that purpose N95 masks can be effective for a bit of time.
In a school setting I really don’t know how effective even a good mask would be over a period of hours. Anecdotely a family friend who is a teacher did wear a mask diligently over the past year and avoided getting sick. In June she ditched the mask because of the heat at school and a low transmission rate. She got COVID and ended up in the hospital two days after school ended. She is ok now, just a little weak still. Can’t say if the mask would have fully protected her or not.
Time for the blue state pansies (and germaphobes everywhere) to stop with the face diapers and get on with their lives. Anyone still wearing a cloth or disposable mask should be treated like the fools they are.