is this normal?

Lots of people do this; better to hit things than people or hurt yourself. Problems could arise if you are damaging furniture etc that does not belong to you. If this is worrying you see a counselor of some kind.

ok thanks my teacher has already found out and contacted one but isn't that going to make me look different and unusual to everyone else eg. all the normal people?

These things are usually done discreetly. Anyhow, you are a 'normal' person. If you need help, get it. Never mind what people think. Is this a genuine set of questions, or are you just trolling for attention?

There's nothing wrong with anger, but when it's expressed by hurting people or things, then it needs to be dealt with.

Sounds like you are going to be confronted by authorities about how you are expressing your anger. Find an anger management class and enroll in it before the court orders you to. (that's coming, you know)

"Normal"?
You have behavioural-issues.
Let them flow and someone will get hurt.
Acknowledge them, then vanquish them.