It is important to be responsible while at school because what you do during that time not only affects your education and your future, it can affect the education and future of others.
Explanation: When you do things in school with obnoxious or unwanted behavior, enough so, that the teacher has to interrupt class to warn you, you take time out of the lesson, which could leave others to have to study more at home, or stay after class to ask a question. Then those who stay after class take up the next class's time and so on and so forth. Along with that, responsibility doesn't just mean behaving, it means doing the work when it needs to be done. Not doing so can wreck your future. Hence, why it is important to always take into account how your behavior and choices have to be considered during a school day, so as to not poorly affect yours or another's future. Hope this helps :)