From the "Assignments" tab on your Dashboard, you can see how many students have completed each assignment. View individual student scores for each assignment that you send by clicking on the name of the lesson or thumbnail. You can also click on the three dots to the right of any assignment to see all student scores for an assignment.
To see all the work that a single student has done, go to your Classrooms tab and select a classroom. Click on the name of a student in your class. You will see a report of all the work they have done.