I agree with you entirely. As teachers, we are supposed to be able to tell an external agent precisely what grade every single child is currently working at. That means that we have to have knowledge of the grading of every topic, and how each topic escalates through the grades. If we can do that, then surely an experienced examiner will also have the knowledge of the requirements for each grade. It should, therefore, be easy to determine the grade boundaries in advance. And if that leads to year on year increases, then Well Done Kids!