With Google Apps you also get Google Groups. This allows you to create simple email addresses that connect to large amounts of people. You can make groups for all your staff by grade level, subject, building, and such. The same can be done for student and parent accounts. Once you have your groups, you can easily send a message or share a document with everyone in that group by using the email address for the group.
Based on your needs you can create these groups manually, through Active Directory sync, or by using the Google Apps API.
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