No, Airlines or FTO's will not look at your behaviour record in school. They will look at your grades however.
We all act up to a greater or lesser degree in School, i think its part of the growing up process. However, if you want to be a Pilot you will have to mature a bit in the next few years, or else you will be "found out". There is a lot of classroom work involved in pilot training, and if you act up in these classes, then you will be asked to leave, and not return.
If you say you can knuckle down, etc. then man up and do it. Hammer out your GCSE's, get the best grades you possibly can, then onto A-Levels and do the same. Learn some self discipline - it will serve you well in your future career. Remember, when you do eventually get to the type rating stage, you will be back in the classroom, except there will be a lot of money riding on you by that point. How do you think the Airline / Bank that is sponsoring you will feel if you get binned for being a bit of a div in class?
And before you ask, I was no angel in School. I had my fair few bollockings and detentions...