The algorithm of the Admission Postbac procedure is a Truth Telling mechanism.
- a) A terminale (final year of secondary school/highschool) student will gain an advantage by classing his or her choices in the order that they are truly preferred.
- b) In reality, this reasoning assumes that the terminale student knows his or her true preferences, something that is not always verified.
For example, consider lycée (secondary school/highschool) X: if candidate B is classed ahead of candidate A when in fact X actually preferred A, this could be several things:
- a) either A ranked X fairly low on his or her choice list and was at any rate accepted into a lycée Y that he or she preferred, and as in this case, having put A before B (which reflects the truth) would not have changed anything;;
- b) or A preferred X , but A and B are assigned to X anyway, and once again the truth would not have hurt;
- c) or A preferred X, B as well, and being that X chose B, it’s B who integrates X and not A - in this case, communicating the truth would have been strictly better for X!
In considering other possible outcomes related to the above example, we notice generally that for most outcomes, to put A ahead of B yields a value greater than or equal to X than does the reverse, which perfectly illustrates that it is of the upmost importance to be honest, and supports the jargon of “game theory” that the "incentive-compatibility constraint" is verified.
For candidate A then: Suppose that he or she classes Y ahead of X (Y can represent a prépa (Preparatory class) and not just a lycée (secondary school/highscool)) when he actually prefers X to Y.
- a) Either his or her candidature only gives access to Y, and he or she might as well have put X ahead of Y without changing the result;
- b) or he or she only had access to X, and again here being truthful would not have changed anything;
- c) or, his or her candidature allowed access to both X and Y, in which case the student will be assigned to Y, whereas he or she could have received X if his or her true preferences had actually been revealed.
The only risk that remains for the candidate: to have overestimated his or her level and have chosen only those academic institutions that did not ultimately offer acceptance.
The best case scenario would be if terminale students could classify without limit all the formations by which they were interested via the Admission postbac website but this is not the case since the maximum limit is 12 choices per division.