The students that appear in your ASSISTments assignment report come directly from your LMS (Google Classroom or Canvas) account roster. If you want to make changes to your student roster, you have to do so within your LMS. Once you do so, follow these steps:
1. Create an assignment in ASSISTments and click "assign" (either through Google Classroom or Canvas)
2. When you click assign, you will be taken to a pop-up that asks you to select which class to assign to. You will see the option to click "Synchronize with Google Classroom" or "Synchronize with Canvas" when you reach the assigning screen.
3. Press that button and your rosters will update.