“Besides, don’t blanks have a paper wad that gets blown out at high speed?”
Yes - or plastic ones. Every once in awhile some kid will goof off and pretend suicide - and I have heard of them accidently killing themselves when the wad goes through their skull.
For us showbizzy types, there was a fairly notorious incident when Audie Murphy shot blanks at close range at Tony Curtis on a film set. The impact caused Curtis to collapse and Murphy thought he had killed him. He was extremely apologetic but Curtis never got over it.
This “teacher” belongs in jail.