Beginning in the 2012-2013 school year, changing your password on the school network will automatically update your Google Mail / Apps password.
In order to change/synchronize your password, log on to any school computer
and then hold the CTRL + ALT + DEL keys. From the menu on the screen, select Change a Password. Your old password is the one you used to log on to windows. The new password must be at least 8 characters long and will need to be typed twice.
This process will change both your windows password and your Google Mail / Apps password.
If you are having trouble remembering passwords see how How Chuck Norris Chooses a Password