MOE has been doing this type of test for many years. They are trying to gauge the overall standard of the pupils. From my understanding, different levels are tested randomly in different years. One of my students told me that it was a surprise test so that the pupils would not be able to prepare for it. In fact, my student told me that most of her friends decided to purposely do badly in the test cos they thought that if they did well, MOE would raise the standard. My student thought that she and her friends were doing their juniors a favour.