I posted similar question for Forest School. Monstermuffin has provided a thread you can find onviewtopic.php?f=31&t=17820
The interviewer provided me with a brochure/leaflet to read whilst he questioned my DS.
As a parent, I asked questions about the extra curriculum activities (timing and sports offered; music). And I also added few things my son forgot to mention about his hobbies and what other sports he might take on next year. He also asked if he was taking any other exams (grammar schools, indies, other sport selective school...)