To the contrary, I know many examples of young people who rock on exams precisely because they learn to pursue curiosity rather than to fulfill minimal school requirements. How useful an examination is depends on how it is designed and administered. How influential examinations are in an overall educational system depends on what incentives are attached to exams and what rewards and opportunities are available to learners irrespective of exams.

Albert Einstein had an interesting account of his school experiences in his longest autobiographical writing, the introductory section of a book I grew up having in my home library (because my dad bought the book when he was a student of the philosophy of science).

http://learninfreedom.org/Nobel_hates_school.html

The examination system that Einstein encountered as a student in Switzerland actually allowed him to spend minimal time getting ready for examinations and most of his time independently pursuing his interest in physics. As Einstein wrote, "There were altogether only two examinations; aside from these, one could just about do as one pleased." If his school grades had been based more on daily homework assignments (as in the United States), then he probably would have seen his "holy curiosity of inquiry" entirely strangled by the school system, to use his words.