How do you say classroom in french?

Class (an hour-long lesson with the teacher) is translated 'le cours' - Class (all the pupils attending the course in the same classroom at some given moment) is 'la classe'

Examples: he fell asleep during French class > il s'est endormi pendant le cours de français.

Il y a beaucoup d'élèves dans la classe de mademoiselle Dupont > there are many pupils in miss Dupont's class.