Yes, you can -- but this action cannot be undone, so please only delete students you no longer need any information on (data associated with the account will also be deleted).
On the bottom of the left panel, you will see a blue button, "+ Add / Edit Students":
When you click this button, the left panel will expand. Select the student you want to delete. At the bottom of the "Edit Student" pop-up, select the button "Delete Student":
Then, select "Confirm Delete" to delete the student: