To delete a student from your class, go to your "Manage Classes" page. Click the "Manage Students" button for the class in which the student you wish to delete is enrolled. This page will help you manage students' accounts.
Scroll down the list to find the name of the student you wish to delete, then click the trash can icon on the far right of that student's row.
Note: This will not permanently delete the student's account but will remove them from your class. All of their assignments submitted in your class will be deleted, as well.