In our interviews, we had two parts.
Part A, they ask about being a prefect. Questions that may arise include: Why do you want to be a prefect? What's a good prefect? What responsibilities do you think you will hold as a prefect?
Part B, for us anyway, was all about you. They asked questions about what you do in your free time, if you had a time machine what time would you go back to, and a lot more questions is know more about you.