Hitting back only works if it's your first response. If you've already led on a ton of times, then hitting back seems like an escalation. It has to come out of nowhere in order to work. Also, don't hit back without really meaning it, you have to have the 'will of the warrior' and hit like your life depends on it. Unfortunately, you will probably get expelled if you do this now, because any bully willing to push someone that far is likely going to make an even bigger joke out of getting you expelled for fighting back.
So if you are willing to accept the consequences for YOU hitting THEM, and you are willing to go 110% of the distance in the fight, by all means go for it. Otherwise, just change classes or whatever and understand that high school will be over soon and you'll never see them again... until they are pumping your gas one day.