There is a time to ignore the bully, a time to resist the bully and a time to put the bully on the floor. The wisdom of age and experience teach you when a particular response is appropriate.

Attack with a ruler is a time for moderate resistance. The ruler is a weapon, albet a minor one depending on the area struck or jabbed.

Attack with a fork or knife is time for violent response, regardless of the school policy.

The school is responsible for providing a safe environment for education. When the school fails to provide safety, a persons rights, even a minors, to protect themselves from harm comes into play.

Words, minor shoves or hostile looks are not appropriate for a violent response. They are a time to pity the bully for the unhappy life he/she must live that make him/her so.
"If you're gonna be stupid, you better be tough."