for a silence to fall, fall silent, for a hush to fall, become quiet, to deaden

classroom

to begin

examination, exam, test / quiz

(education) instruction that takes place outside of a classroom (field trip, etc.) / (education) class that takes place in its own specialized room instead of homeroom (such as music or cooking)

(law) a bar examination

litmus test

a mock exam

oral examination; oral test

graduation examination