Miguel Guhlin at TCEA has a new blog entry for you if you are leaving your school district and don't wish to abandon years of hard work, emails, files, and Google Classroom courses.
He starts with helping you to clean up your email, then doing the same with your Google Drive. Then, he shows you how to copy your Google content over to your personal Google account (which is limited to 15GB unless you have a paid account). The process could take a week, so be on the lookout for an email from Google telling you when your G suite data has transferred over. These processes are separate for Gmail and for Google Drive.
You may view Miguel's post here.