It’s obvious, but it still needs saying: the way you behave affects your learning. If you constantly shout out, wander around the classroom, or annoy your classmates, not only does it make it harder for your teacher to teach, it makes it harder for you, and for the rest of your class to learn. Is that fair to them?
Why is it worth changing your behaviour? Well, think about all the Olympic medallists from last year. If they had messed about instead of training hard, they would never have won their Olympic medals.
Maybe you can’t win a medal for your school work, and maybe you won’t get a postbox painted gold in your honour just because you try hard in class, but if your teacher can see that you are making an effort you may get housepoints, certificates, merits, or whatever other rewards your school hands out.