> ... because the notation system changes from there: instead of gaining points when giving the right answer, > you lose points for every wrong one ...

This is not a general rule, where I was it was still "positive scoring" (get points for what you solve). But I agree with the rest: the notation gets much harsher and it's a way to toughen up previously top of the class students who were used to have a rather easy time before.

The regular oral tests ("colles") are also part of that...