Primary and Junior High School Act Article 25

Public schools may jointly appoint a teacher with another school because of cooperation between the schools, course needs, or special circumstances, and the teacher shall be appointed on a full-time basis in one of the schools. The regulations governing the criteria for jointly appointing teachers and the associated ratio limits, the teachers’ rights and obligations, and other related matters shall be prescribed by the central competent authority.
中文原文 國民教育法第25條
公立學校因校際合作、課程需要或有特殊情形者,得與他校合聘教師,並於一校專任;合聘教師之條件、比率限制、教師之權利義務及其他應遵行事項之辦法,由中央主管機關定之。

English translation for reference only; the Chinese text prevails. Not legal advice.