A junior high school / middle school — the lower secondary education institution, typically covering grades 7–9.
娘は来年、中学校に入学する予定だ。
My daughter is scheduled to enter junior high school next year.
中学校の先生は授業の準備に忙しい。
Junior high school teachers are busy preparing lessons.
その中学校はスポーツが強いことで知られている。
That junior high school is known for its strong sports program.