1.
principal's office
The office of the school principal (校長). In Japanese schools, a dedicated room where the principal works and receives visitors.
校長室 is a compound of 校長 (principal) + 室 (room). This follows the common Japanese pattern of [role] + 室 to name offices.
Usage
Being called to the 校長室 can imply being in trouble, similar to the English expression "sent to the principal's office." The room is also used for meetings with parents and official visitors.
SIMILAR 〜室 COMPOUNDS: