1.
school
An educational institution. Can refer to any level: elementary school (小学校), middle school (中学校), high school (高校/高等学校), or the general concept of school as a place of learning.
学校 is the general term for school. For specific school levels, Japanese uses: 小学校 (elementary), 中学校 (middle school), 高校 or 高等学校 (high school), 大学 (university). The particle に is used for the destination: 学校に行く (go to school).