"..exchange of teaching materials between a student and teacher geographically remote from each other.
The student obtains a textbook locally, and lesson plans, lecture notes and problem sets are sent by the instructor to the student. The student sends completed assignments back to the instructor for grading, and exams are administered by a proctor local to the student." - From "What is a Correspondence Course?" on Wisegeek website 2011092
"In the United States William Rainey Harper, first president of the University of Chicago developed the concept of extended education, whereby the research university had satellite colleges of education in the wider community, and in 1892 he also encouraged the concept of correspondence school courses to further promote education, an idea that was put into practice by Columbia University. - From Wikipedia 20110928
Cropped from photo of "Arabian Gulf (Mar. 18, 2003) -- Postal Clerk ...sorts through 16,000 pounds of mail piled in the ship's hangar bay"
U.S. Navy photo by Photographer's Mate 2nd Class Alicia Tasz. (RELEASED), 18 March 2003
File:US Navy 030318-N-4048T-007 Postal Clerk 3rd Class Samantha Miller sorts through 16,000 pounds of mail piled in the ship's hangar bay.jpg - Wikimedia Commons:
"This Image was released by the United States Navy with the ID 030318-N-4048T-007.
This file is a work of a sailor or employee of the U.S. Navy, taken or made during the course of the person's official duties. As a work of the U.S. federal government, the image is in the public domain."