from
The Collaborative International Dictionary of English v.0.48
Correspondence school \Cor`res*pond"ence 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.]