From my experience normal classroom size runs between 23-30 kids. I’ve been retired for 7 years but when I taught kids with EIP’s usually had team teachers,which would account for the two teachers death.
Each state is different. 1 may have been in the hall for some reason as he came in.
Memphis schools are some of the worst, and most violent. Blue City. Police are hated.
We live in the next county over, small town of 7,000. Our schools are small for those grades, plus a private school. Middle/HS combine with the next city. Don’t know about class size. But doors are locked with a buzzer/speaker. Course that would not stop AR 15 rounds.