Private School Act Article 63

The qualifications and age limits for the selection and appointment of principals/presidents and teachers in private schools at all levels and of all types shall follow the regulations prescribed for public schools at corresponding levels and of corresponding types.Principals and teachers mentioned in the preceding paragraph, who have been reviewed, registered, certified, or approved by the school authorities, may have their years of service combined when transferring to public schools for the purpose of determining qualifications and salaries. When handling retirement, death gratuity or bereavement compensation, or severance in public schools, their years of service may also be combined, except for the years already counted for retirement or severance in private schools. The combination of years of service for retirement, death gratuity or bereavement compensation, or severance shall be applicable to principals and teachers who transfer from public schools to private schools.
中文原文 私立學校法第63條
各級、各類私立學校校長、教師之遴聘資格、年齡限制,依公立同級、同類學校之規定。
前項校長、教師,經學校主管機關審定、登記、檢定合格或核定有案者,於轉任公立學校核敘資格及薪給時,其服務年資得合併採計。
其於公立學校辦理退休、撫卹、資遣時,除已在私立學校辦理退休或資遣之年資應予扣除外,其服務年資得合併計算。
前開退休、撫卹、資遣年資之併計,於公立學校校長、教師轉任私立學校時,準用之。

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