User's windows logon credentials are integrated with their Google Apps credentials. In order to keep both accounts in sync, students will not be able to change their passwords. Teachers will only be able to change a password using a windows pc connected to the school network. If a student password needs to be reset, then an administrator will need to generate a helpdesk ticket.
Teacher password reset:
From a Windows PC connected to the school network, select Ctl + Alt + Delete. Fill out the reset password form. This will set both your Windows and Google password.