Ever since its inception, l’X has recruited its students based on the French republican ethos of meritocracy. When recruiting the very first cohorts of the institution, examiners were instructed to judge candidates not only on their acquired knowledge, but also on "their natural aptitude for science and the arts, and the precision and clarity they bring to their answers". It is clear that the aim of the institution has always been to provide high-quality education to the best students, as it was also stipulated that "the candidate who knows the best should naturally be preferred over the one who knows the most". A decree issued on August 24, 1796 provided for the appointment of three to five admissions examiners who would be responsible for selecting candidates during visits throughout the whole of France. In the 19th century, under the Government of National Defense between 1871 and 1872, the number of places open for the competitive entry examination increased from 140 to 280.
The examination for entry into the Ingénieur Polytechnicien Program gradually became more open, and, in 1921, students of other nationalities were permitted to take it for the first time. More recently, in 2000, the number of candidates permitted to take the exam increased to 500, including about 100 places for international candidates. The exam continues to open up through the University Stream, which welcomes around 20 students each year. Since 2017, around 10 places have been reserved for candidates from French Grande École preparatory classes in the BCPST (Biology, Chemistry, Physics and Earth Sciences) track. In the near future, the number of international students admitted each year into the Program is expected to reach 150.