correspondence school

 A school that teaches by correspondence, the instruction being based on printed instruction sheets and the recitation papers written by the student in answer to the questions or requirements of these sheets. In the broadest sense of the term correspondence school may be used to include any educational institution or department for instruction by correspondence, as in a university or other educational bodies, but the term is commonly applied to various educational institutions organized on a commercial basis, some of which offer a large variety of courses in general and technical subjects, conducted by specialists.  [Webster 1913 Suppl.]