All students train together on whatever technique the instructor wishes to demonstrate, regardless of experience. However, students are only responsible for knowing a subset of technique. This subset expands as students gain rank.
Rank is achieved through testing. Testing is conceived as a demonstration of not only practical knowledge of technique, but also a still, receptive and decisive mind. Although there are minimum formal requirements for each rank (such as time), it is ultimately the decision of the instructor and the willingness of the student that determines when testing occurs. The instructor will recommend testing only when the student already performs required technique at the expected level of mastery. Ideally, the testing is really only a demonstration to recognize a stage of the student's development.