When mastery is turned on in gradebooks, this permits multiple skills to be associated with each assignment. In gradebook settings, teachers have the option to check a box in Default Displays to "Group by assignment type" which is helpful, but in the case of teachers using multiple assignments to assess the same the skill, they would also like the ability to "Group by skill" so that they could easily see all the assignments that are assessing particular skill adjacent to one another in the gradebook. Their chief purpose is get a sense for how many times a skill has been assessed within the gradebook without having to visit the Mastery Overview tab, click on a student score and see a list of assignments there.