Need help! Please. to correct apology letter. Very important.

Please correct my letter. This is very important to me as you can probably understand by reading it. Feel free to as as many points and things as you want. I need it to be very apologetic as i have een excluded from my school and i'm writing a letter to the headteacher asking if he will let me back in. Please make its sound very formal replacing any words making them better. How to start the letter, opening paragraph? Shall i make it longer? What words to use to use which are apologetic. I am geniunely sorry for it very much, and i need to make it sound like it. If you think there is another point you can add, please do so. It neeeds to be perfect. And i don't now if the paragraph's are right, should there be more? Also how to finish it off, with faithfully or...? Thank you, i appreciate this very much. P.S> I am 15 yeears old living in the united kingdom if that helps

Dear Mr _(NAME)_

I am writing this letter concerning my recent exclusion from MY SCHOOL)_School. I would like to express my sincerest apologies for my inappropriate actions on Tuesday 16^th November when cannabis was experimented by myself and others.

During the week which I was excluded for, I realised just how much this school mattered to me; and the problem with what I did. How it could affect my future at the school and my future in life. I was very worried and only wished that I wouldn't get excluded permanently. When the decision came that I should be expelled, I was devastated. That was the first time I felt so much failure and disappointment in myself. Now this is probably my last chance to make it back into this school and you cannot believe just how much I need this. I know what I did was wrong. I should never have got involved and it was a stupid and silly mistake. It would mean so much to me if I was allowed back. Whilst I was excluded I regretted being involved in this so much, just praying that you would let me back in. The only thing I'm concentrating on now is my education and making something of myself in the future. MY SCHOOL)_ School is where I started my secondary education and have been studying for the past four years. All my friends are there, and I believe it is the best place to help me accomplish my dreams of a good future. I have already started my GCSE coursework here and to start again at another school, I would find very difficult; especially to fit in with the other students. You can be rest assured that if I was allowed to stay at the school, my mind would be set on achieving well in my studies and being a good student at _.I just want another chance to prove myself.

I would like to once again apologise for my actions. I hope that you will find it in yourself to forgive me and understand that I am not a bad pupil; I just got involved when I shouldn’t have.

Yours, (what shall I put here?)