Well, the prefects at school represent the students. They are normally responsable for running certain things at the school (like school events, or often enforcing discipline) and they normally have special priviliges too. They are either chosen by the staff of the school, or they are voted in by the students.
Thanks, you made it perfectly clear. I think the system is a bit different here, but we have something similar that we call "rappresentanti di istituto" (for the whole school) o "rappresentanti di classe" (if it's just for one class). I hope this helps!