Never heard of them before for support staff, but they have happened for teachers. I guess it depends who it is with and what they ask you, it is somewhat of a concern that the school management is trying to find out what went wrong at the point of you leaving. If you are asked a direct question I'd give a direct answer in as civil a manner as possible depending on the circumstances, if it is a rubber stamping exercise I'd be inclined to refuse to attend, if this is not an option and you feel uncomfortable with the situation just get up and leave.