Use this printable resignation letter if you're leaving your current position to go back to school full-time.
I will be going back to full-time classes this fall to finish off my MBA. Classes start in October.
I don't have to tell you that this is a very time-intensive course of study that will take up most of my time if I'm to do justice to myself. Therefore, I am resigning from my position of telephone sanitizer as of Friday, September 30. By then I expect to have my projects all cleaned up and the slate blanked for my successor. If you assign someone to take over before I leave I'll be happy to work with them to make the transition go smoothly.
My best regards to my friends at (the company) and I'll be keeping them up to date as to my progress.