Let me share 2 tips with you which apply to all school: try to keep him in good mood and good condition.
Good mood may mean going along with your domestic helper (if any, or anyone in good relationship with him). My girl cried non-stop in 2 interviews when not going with our helper. Some schools don't like or allow the helper to attend the interview but at least she can keep your boy emotionally stable when you all go out together.
Good condition means make sure he sleep well and eat well JUST BEFORE interview starts. You have to know your boy's body-clock and do the timing aginst the interview timeslot. Do give him milk or snack if you find him already getting tired just before the interview.