If you've accidentally removed a student from your class, the easiest way to add them back is to use the 'add a student' function.
Step 1: Go to the 'students' tab on the side menu. Click 'add students'. This can be found above or below your class list.
Step 2: A pop up will appear with three ways to add students. We are interested in option 3: 'Add an Individual Student'
Step 3: Enter the first name, last name and email address of the person you deleted and press 'send invite'. This will resend the invite to the student, asking them to join your classroom again.
Note: Make sure you get the email address correct, otherwise you might invite a completely different student! Or no student at all!