[Its.Just.Angie]

Sorry about what happened Anxiety attacks are the worse! And school makes it a lot harder to have in my opinion. It does help to leave to class for awhile til you are more calm. I just ask to go to the bathroom or something, but if they say no.. Just say it's an emergency then they usually (or should) let you go. (Speaking from experience)
Like said above it may be a good idea to say something to your teachers then if it happens again. They will be more lenient with passes and stuff (if you have limited passes per semester or something) or talk to your school counselor about them or when you are having one. It may help if people do know about it (people you trust)

How I deal with them is I usually dim my lights and play music and lay my bed and breathe deeply or play with my dog) Or if at school I go to the bathroom (or a room with no one in it.) and close my eyes and say positive stuff or count in your head as how high you want to count with a breath every number (it helps not thinking about the anxiety attack)
Or get your mind somewhere else. (Place where you dream to go, or go to imaginary world or something to get you side tracked that isn't stressful)

To find where they are coming from can be really hard. But you have to think really deep to find out what exactly triggered it. It's hard for me to even find out. Or go to a professional and you could talk about it. They help with that kind of stuff. Medication can help a little bit. It doesn't make them disappear, but it does help and you won't be always on the edge.

This is nothing to be embarrassed about. They are awful to have! It you can't control them so it isn't your fault to feel this way. I'm sorry on what you have to go through. Feel free to PM/VM me hope it gets better for you!