In early life he was acquainted with Sir Walter Scott, and was one of those who read Waverley before publication.
Failing to receive adequate support, however, the school was ultimately sold to the kirk session of New Greyfriars.
Simpson continued to support the cause of non-sectarian education, and lectured in England and Scotland on the subject.
In 1837 he was a witness before the committee of the House of Commons on national education in Ireland, and his appearance lasted seven days.
Simpson published A Visit to Flanders and the Field of Waterloo, Edinburgh, 1815, which rapidly went through nine editions.