The English expression “to fail (something),” like an exam, is échouer (à quelque chose) in French.
Example:
J’ai échoué à mon examen.
I failed my exam.
Alongside échouer, there’s an informal verb used fairly frequently in French that you might want to learn: couler.
Examples:
J’ai coulé mon année.
I flunked at school (my school year).
T’as coulé ton examen?!
You flunked your exam?!
T’as in the example above is an informal pronunciation of tu as.
You’ll especially hear the informal verb couler used in this sense when talking about flunking tests and exams at school, or even an entire school year.
[This entry was inspired by the character Michel in La Galère, season 3, episode 9, Radio-Canada, Montreal, 15 November 2010.]