Yes, you can change the passwords for your students in your user account.
Find the student you want to remove by clicking on 'English Every Day' in the menu on the left, then on 'Classes'. Then select the student's current class.
Click on the name of the student. It'll take you to their page with the English Every Day statistics and the class they're in.
Right under the students name you have different options. Click on "Change password" and enter a new password for the student. Confirm by clicking 'submit'.