In my last school, student voice was not viewed to be effective. I implemented a new school council to ensure that every student is given an opportunity to air their views at least once per half term. This created big engagement with the student body and it was reported that students felt they were finally being listened to. It also is very good if you are being inspected.
As the member of staff responsible for school council, it took a lot of time to research and plan this. However, after it was planned it only required 1 assembly from me to explain it to the students. After that the time demands are: two lunchtimes per half term to supervise the student council meetings, one form time per half term for each form group to air their views, and one meeting per half term for the principal and the heads of year.
If you have any questions about the reasoning behind each part, how to implement this, or any questions at all, please ask.