Unexpected. s/
Something most of us already knew.
Good masks properly worn give some protection but it is only short term (best studies showed about 15-30 minutes in close contact with an infected person). No basic mask (N95) is going to protect you if you are sitting around for an hour or so, exposed to COVID.
Most kids had worthless paper masks, they did not wear them correctly and they were in close contact with each other for extended periods. It is not surprising that the masks were useless. Unfortunately at least some of these kids who got COVID in schools will have some permanent heart and lung damage from the toxic spike protein in the virus. The same spike protein is in the vaccine although it appears to be slightly less toxic, for whatever that is worth.