Once he was a priest he exercised his ministry at a parish of Ruan and continued his studies, especially focused on grammar.
He gave up his priestly functions near 1540 when Paris, having heard of his competence, called him for teaching grammar in diverse locations.
While he was directing the School at Nevers, he came back to Paris where he met Robert Estienne.
Estienne was a lexicographer and Protestant printer, who edited the works of Mathurin Cordier and convinced him to convert to Protestantism.
The state paid for the living costs of the pupils, who were allowed to confess or go on with their ministries.
Corderius was a brilliant pedagogian and grammarian who contributed much to the recognition of pedagogy, rhetoric, and linguistics.
He possessed special tact and liking for teaching children, and wrote several books for them; the most famous is his Colloquia (Colloquiorum scholasticorum libri quatuor), which has passed through innumerable editions, and was used in schools for three centuries after his time.