• 学校がっこう — school
• 校長こうちょう — principal
• 校庭こうてい — schoolyard
• 校舎こうしゃ — school building
• 登校とうこう — going to school
• 休校きゅうこう — school closure

校 is strongly tied to schools (学校, 校長, 登校), but it also appears in 校正, meaning “proofreading / correcting text.” So this kanji connects both “school learning” and “checking / correcting.”