Change Administrator or Teacher password:
Login to your Administrator or Teacher account
Click My Profile after clicking on your Avatar on the top right of the screen
Scroll down to the bottom of the page and then enter the new password
Change Student's password
From the Administrator's page:
Click Students
Select a student and enter the student's statistics page
Click Actions -> Change password
From the student's page:
Login to the student account
Click My Profile after clicking on your Avatar on the top right of the screen
Scroll down to the bottom of the page and then enter the new password