Appletons' Cyclopaedia of American Biography stated that Plessis "studied classics in the College de Montreal, but refused to continue his education, and his father, who was a blacksmith, set him to work at the forge. After a short experience at manual labour, he consented to enter the Petit Seminaire of Quebec in 1780. On finishing his course he taught belles-lettres and rhetoric in the College of Montreal, and notwithstanding his youth became secretary to Bishop Briand. He was ordained priest on 29 Nov., 1786".