Graffitoed inscription found on the wall of a Roman villa excavated in the early 1990's in the Rhineland just south of Remagen (a farm settlement between the colonies of Colonia Agrippinensis and Confluentes, probably dating to the time of Claudius. This is from memory, so forgive me if it is a bit paraphrased:

1st Boy: I don't want to go to school; the master beats me!
2nd Boy: Rightly! Only because you're so dumb.
1st Boy: I'll beat you myself if you say that again!

This is the earliest record of school violence I know of, though certainly it must have existed earlier.