Should older students take care of younger students on field trips?

In my school, whenever we went out for anything each older student had to take care of a younger kid. This meant on field trips, we had to follow one, maybe two kid(s) and we wouldn't have time for ourselves to play. Not only do we not get paid to do this, we end up doing the teacher's job when we're supposed to be having fun. In my class we used to complain about it a lot and since we have to write an essay on this for coursework there's not much to be written other than oh yeah I followed a kid around all day. Which leads to decreased marks and therefore a lower grade.