Most studies on the role of Mexico’s National Union of Education Workers (SNTE) focus on its political activism and the insurgency of its factions. However, there has been limited analysis of the role of the union leadership in defining standards for selecting and recruiting school principals and zone supervisors, who are the schools’ leaders. This chapter addresses this relationship, documenting how Latin America’s largest corporate union colonized the management of basic education in Mexico despite several governments trying to diminish its power. This confederation goes beyond what several authors qualify as interest groups. It is a solid political machine. Besides, the leadership controls the professional trajectory of teachers and is perhaps an atypical reference in Latin America between the education system administration’s development and school leaders’ appointments. There is an overlap in decision-making between the civil service of the SEP that arrives with each government and the authorities promoted by the SNTE that, in general, remain for a long time in office. The chapter includes relevant lessons for Mexico and the rest of Latin America.