Medically speaking, it counts as a panic attack if you have four or more symptoms from the following:
* irregular heartbeat or rapid heart rate
* breathlessness/hyperventilation
* feeling unsteady, dizzy, light-headed or faint
* trembling or shaking
* sweating
* having a hot flush or chills
* chest pain or discomfort
* numbness or tingling sensations
* feeling as if you or surroundings are unreal
* nausea or churning stomach
* choking
* fear of dying
* fear of losing control or going crazy.
This nicked from the channel 4 website, but it's in lots of different places and seems to be the agreed list. Basically any combination of four or more off this list = panic attack.
If you have fewer than 4 symptoms, I believe it's a "limited symptom" panic attack, or an anxiety attack. It does sound like you might be having either panic or anxiety attacks.
I'm not a medic or anything, but I get panic attacks sometimes and this is the stuff that I've been told by people who know more than I do.
Sadly this is where my knowledge peters out. I have yet to deal with my own stuff by any other means but avoidance, and from the sound of it that's not something that it's going to be practical or possible for you to do.
If it *is* distressing you then try and talk to someone (do you have a school counsellor or anything?) who might be able to provide more help...it might well be possible to just expose yourself more and more to the room and the teacher that's causing the anxiety, but it depends on how much it's upsetting you...if it's really frightening you then I would get help from someone else if you can.
This is quite possibly of no use to you at all, and if so then please feel free to send me off with a flea in my ear, but either way I hope you sort things out one way or the other soon.