In exchange the ESC spend their schooling from two to three years and organize themselves into a network with tests and subjects common to the written competitions.
If HEC and ESCP join this system, ESSEC positions itself as a challenger and keeps its own preparatory classes and competitions. To be at the level of its competitors, however ESSEC passes its schooling from two to three years from the year 1947.
The first class has 7 students and the studies last two years. The curriculum does not denote by its originality by structuring itself around a set of law / accounting / languages / technique.
It is through the introduction of Christian moral values that ESSEC intends to stand out: students attend the apologetics conference each week at the Sainte Geneviève School Chapel.
A preparatory class for the exam was set up in 1941, which became a competition in 1947, the number of candidates permitting it.
However, ESSEC refuses to join the unified system of écoles de commerce (ESC) established by the decree of 3 December 1947 the State now supports the implementation of preparatory classes on the territory (there were thirty at the time, for a twenty ESC).
This situation lasts until 1951, when ESSEC closed its preparatory classes to open to candidates of the public preparatory classes, more numerous, and thus avoid the marginalisation of its competition.
If the ESSEC management criticizes the university model, it understands that the legitimacy of the school goes through increased recognition of the state, which recognizes it in 1942 and aims to graduate from 1962.The arrival of the hollow classes of 1914-1918 and the economic crisis further increase the difficulty of the situation.The school is obliged to accept baccalaureate, non-bachelors on exam and even free auditors who come to take courses without the diploma, for a tuition fee.The school hardly survives the mobilizations of the war: in 1914, it counts only four pupils in first year and two in second. The third optional year is closed and the school only regains financial stability from 1920 where it welcomes more than 50 students in first year and 150 in 1930.In 1923, alumni association is created: a solidarity fund for widows and orphans of war is being set up.Technical education (calligraphy, shorthand, writing of commercial documents) is combined with scientific education (physics, chemistry, factory visits).