A school building or schoolhouse (the building that houses classrooms, offices, etc.).
新しい校舎が完成して、来月から授業が始まる。
The new school building has been completed and classes will start from next month.
古い校舎は耐震補強が必要だ。
The old school building needs seismic reinforcement.
放課後、校舎の前で友達と待ち合わせした。
After school, I met my friends in front of the school building.