study hall

noun2

1. •
   (US, Canada) A class period, usually in boarding school or high school, where students are afforded the time for independent study and homework assignments, as part of the curriculum or after hours, the last notably as a punishment called detention.

   • He finished drafting his essay in study hall.
2. •
   (US, Canada) The classroom or other school hall used for such a purpose.

   • The supervising teacher's stern expression at the front of the drab study hall left little doubt that no nonsense would be tolerated there.