He founded and ran the exclusive Mr Mundell's school in the West Bow of Edinburgh, from 1735 to 1762.
Agnes Mundell continued her son's business upon his death.
Mundell's school taught the humanities, to boys and girls, primarily in Latin.
It served the wealthiest residents of Edinburgh, who were concentrated in the Lawnmarket.
According to an official List of scholars educated by the Late Mr. James Mundell, printed in 1789 in Edinburgh by Mundell and Wilson, 568 boys and 94 girls attended the school during its years in operation.