Act Governing the Appointment of Educators Article 27

Junior high and elementary school principals shall be selected openly from the qualified candidates except those who hold the current positions in accordance with the decrees.The same shall be applied to high school teachers except the allocated ones.
中文原文 教育人員任用條例第27條
國民中、小學校長之遴選,除依法兼任者外,應就合格人員以公開方式甄選之。
中等學校教師,除分發者外,亦同。

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