It sounds like you're using the wrong tactic. It's never a good idea to try using logic on people like that; all too often, they're just too stupid to understand you. Treat it like a Pokemon battle. If you're suddenly confronted with a high level Pokemon, you don't try to battle it out right. You use status effects to your advantage.
Your first choice is always Teleport. If possible, leave, preferably before they notice you. If they have Mean Look, Shadow Tag, or Arena Trap, unlike a Pokemon battle, use metronome. Approach a teacher and talk to them. They might not give you much time, but it might just be enough for the bullies to leave. If that's not an option, try Dig or Fly to buy some extra time. Try to join a conversation nearby, to discourage them. If they can't get to you easily, they'll leave.
They respond to physical signs of strength. That means you want to show them that you're strong. The best way to do that is simply to act confident and aggressive around them. If you act like you're going to go rip somebody's face of, they'll stay away from you. To put it in Pokemon terms, use astonish, make them flinch.
You could also try to confuse them. If a predator sees something it doesn't recognize, ninety percent of the time, it will avoid it. Use really big words around them, especially ones that sound like they might be complements. If you're really lucky, they might even start arguing about what the words mean, giving you time to run away. This is a perfect strategy if you know a foreign language. Just speak that language to them, and try to confuse them that way.
Try paralyzing or freezing them. Say something so off topic that they forget what the original topic was. This can be nigh on impossible to pull off, but if it works, it's extremely effective.
When things get desperate, poison them. Say or do something that seems innocent to random passerby, but is very wounding to them. This can require some research beforehand, but is very useful if you know what you're doing.
One thing you never want to do is to try to burn them. They have Flash Fire, so that will only make them angrier and give them more power.
There are two things you want to have: versatility and the ability to improvise. Have all of these, and more, if you can think of them, ready to use whenever you might need them, and learn how to adapt them to the situation. It might sound silly, but practicing this can be a very good thing.
