Throughout much of the 1880s , Mackenzie taught at the elementary and secondary level in Flint , Michigan ; by 1888 , he had been promoted to the position of Superintendent .
By 1881 , David Mackenzie had earned his teaching credentials and a Master 's degree .
Throughout much of the 1880s , David Mackenzie taught at the elementary and secondary level in Flint , Michigan ; by 1888 , David Mackenzie had been promoted to the position of Superintendent .
By 1881 , David Mackenzie had earned his teaching credentials and a Master 's degree .