Let's assume you are over the emotions involved in all this and now need to know, "How can I bring all my documents, messages and other data in Google Apps with me before this happens?"
To transfer your documents...
Google Takeout is a tool that let's you download a copy of almost all your Google Apps data on the web. You can also choose to just download the data you need, such as Drive and YouTube.
It downloads all of your online stuff as one LARGE file, depending on how many things you have uploaded to the cloud. You can use that downloaded folder to transfer (upload) your data and information to another school or personal Google Account in the future.
Google's Data Liberation site dataliberation.org provides additional information to help save/move your Google Apps data upon leaving a school district.
The most simple way to transfer your Google Drive documents to a new account is to put all of your documents in one folder, share that folder with your personal Google account, and then Make a copy of that folder in your personal account. You cannot transfer ownership from a document out of a Google Apps district, only SHARE and then Make a copy.
Google Takeout does not download your Gmail messages. If you want to download your messages, use Gmail's Mail Fetcher to migrate and old and new messages from your Google Apps account into a personal Gmail account.
First, take a look at this post from Miguel Guhlin's blog on transferring email from Google Apps to personal Gmail.
Second option, the Google Apps Migrator from Backupify (3rd Party Website). It is a free tool that should let you transfer your entire Google Apps account to another Google Apps account all at once - Backupify is currently working on making this available to transfer all your data OUT of a Google Apps account to and Personal Google account, so if it does not work for you just yet, try it the next time you need a tool.
Screenshot of downloading just Drive data using Google Takeout