So you have set Schoolwork for your class group and enabled the Track work turned-in option. This means that you want to track if each student physically turns-in their work to you. Let's take a look how.
1. Click on the Assignments tile in your class group
2. In the list of Assignments that you have set the class group locate the Schoolwork. You will notice a Turned-in section which will display how many students have turned-in their work. Click on this to display the Track Schoolwork panel.
3. You will notice that all students will have the Turned-in toggle enabled. You only need to disable students who have not turned-in their work. You also have the option of selecting a Late option and giving a Reason for late turn-in. The Comments box is optional and can be used to record any additional information such as a reason for late turn-in or comments about the work.
4. Once you are done click the Save button.