You seemed to be on top of it in your first post, and Ohfor07 gave such excellent suggestions, too.
A family story told how my grandma, as a child, had a chair pulled out from behind her when she was just sitting down...as a joke.
Teacher got a handful of snow and packed grandma's mouth, because she had bitten through her tongue.
I don't recall hearing any more details of the story, but grandma herself did not show any permanent injury...thank goodness...unless she had misgivings about smart alecs.