IPA: /ˈklæs.rum/
KK: /ˈklæsˌrum/
A room in a school where students learn and teachers teach.
The teacher arranged the desks in the classroom for the group activity.
Classroom → It is formed from "class" (from Latin *classis*, meaning a division or group) and "room" (from Old English *rum*, meaning space or area). A classroom is a space designated for a group of students to learn together.
Think of a 'class' as a group of students learning in a designated 'room' — that's what a classroom is.
No commonly confused words.