Foundation and first constructions (1630–1792)

In 1630, the consuls of Lectoure (municipal councilors), under the leadership of Marshal Antoine de Roquelaure, in agreement with Bishop Jean d'Estresse, decided to found a Catholic college. This project was part of the Catholic Counter-Reformation and aimed to strengthen religious education in the region. The Congregation of the Priests of Christian Doctrine, simply called the Doctrinaire Fathers, was chosen to administer the institution, following discussions with other orders such as the Jesuits and the Oratorians. The institution offered instruction ranging from literacy to philosophy, including Latin, Greek, mathematics, and science. It reflected the fathers' commitment to transmitting the Christian faith in an accessible and understandable manner. They favored a pedagogy based on persuasion and emulation rather than reprimand, thus distinguishing themselves from other teaching orders of the time.

The land for the construction belonged to an old medieval hospital known as the "Hospital of the Holy Spirit." The vaulted cellar of the main wing of the building is the only remaining part of this old building with a central stone pillar. From the beginning, the building had the "U"-shaped layout of the main building, with a courtyard opening onto Rue Nationale.

It was extensively remodeled in the mid-18th century and included a chapel located at the southern end of the west wing, and an inner courtyard that served as a playground. The first floor was reserved for the priests' lodgings and the dormitory for the students, exclusively for boys.

From municipal college to Maréchal-Lannes high school (1809–1967)

In 1809, the building was reassigned as a municipal college. The fire of 1899 had significant repercussions on the college's architecture. Following this disaster, the college was completely restored. The reconstruction work was completed in 1901, when the establishment was transferred to the State. During this restoration, two buildings were added on either side of the entrance portico, thus closing off the courtyard and serving as a concierge and visiting room.

The Collège des Doctrinaires de Lectoure officially became the Collège Maréchal-Lannes in 1943, during the Second World War. It closed permanently in 1967. Jean Lannes (1769–1809), Duke of Montebello, was one of Napoleon I's most brilliant marshals. He was born in Lectoure, which justifies this local tribute during a time of war, at a time when historical military figures were remobilized to strengthen patriotic sentiment.