Primary and Junior High School Act Article 23

In principle, public schools shall have small classes and each class shall have a teacher serving as its homeroom teacher on a part-time basis. Small schools may consider increasing the number of teaching positions. The regulations governing class sizes and staffing shall be prescribed by the central competent authority.The regulations governing staffing referred to in the preceding paragraph may be prescribed based on the number of students’ learning periods and the number of hours the teachers teach.The special municipality or county (city) competent authority may consider a school’s needs, and in accordance with the provisions of the regulations referred to in Paragraph 1 and remaining within a fixed proportion of the full-time staff complement of the entire school, shall use all of the fulltime personnel staffing budget not being spent because of staff vacancies to pay expenses to employ necessary teaching staff for the school.
中文原文 國民教育法第23條
公立學校以採小班制為原則,每班置導師一人,由教師兼任,學校規模較小者,得酌予增加教師員額;其班級編制及教職員員額編制準則,由中央主管機關定之。
前項準則所定教師員額編制,得視學生學習節數及教師授課節數定之。
直轄市、縣(市)主管機關得視需要,依第一項準則規定,在不超過全校教師員額編制數一定比率範圍內,將專任員額控留,其所控留之員額經費,應全數支用於改聘教學人力所需之相關費用。

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