Unfortunately what happens in most schools is both people get on trouble, not solely the instigator but even if the victim does the bare minimum for self-defense.
According to your story, you did not take it over the line, you were just defending yourself.
For example, in New Jersey, there was a law effective last September:
It should be noted that all due process rights will be observed; however, the burden of proof in a disputed case will rest with the bully, not the victim. The victim will not be expected to prove that he/she was bullied, intimidated or harassed; the bully will be expected to prove that he/she did not violate the policy to the satisfaction of the investigating officer.
As you can see, it's pretty much bullstuff. The schools will try to end bullying with crazy laws (failing to do so anyway) at the cost of justice.
This law was actually implemented in response to the incident with Tyler Clementi, the student who jumped off the GW bridge because of begin bullied -- and the law doesn't even apply to colleges and universities like the one he was attending. Don't forget, we're also grinding the idea of burden of evidence (in bullying) to a halt just because of one person's incident among ~1.35 million students in public schools.
