Your Google Apps account password is Sync'd to your SFUSD network account. Therefore, if you change your SFUSD network account, your Google Apps account will also be changed.
To change your account password, follow this link: Change password.
If you have difficulties, you may call the SFUSD DoT Help Desk at 415-241-6476. option 1, and they can change you password for your. Please keep in mind that when you phone, you will be asked to confirm your identity.