I have been using Google Doc's for a couple of years.  I found myself reverting back to MS Office now that Dropbox has such a large storage capacity. I'm up to 8.25G for Free. You can increase your storage capacity by referring your friends to join. Just send them a shared file or folder and you get a 250M storage increase on your account.

Another technology that you might want to have a look at is ZoHo.com this is a similar system to Google Docs. There are a few more features and the system is organized in a friend format. They offer a one stop shop, with several educational tools. This might be a good platform for k-12 classes?

Collaboration: Chat, Mail Suite, Discussions, Meeting, Projects, Share, Wiki.

Business: Assist Books, BugTracker, Creator CRM,  Invoice, People Recruit, Reports.

Productivity: Calendar, Docs, Notebook, Planner, Sheets Show Writer.