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temporary absence from school
病気療養のため一年間休学することを決めた。
I decided to take a year off from school for medical treatment.
休学届を提出するには保護者の同意書が必要だ。
A guardian's consent form is required to submit a leave of absence.
休学中に海外でボランティア活動をしていたそうだ。
It seems they did volunteer work overseas during their leave.