The 1917 Constitution strengthened the Mexican state's power in education, undermining the power of the Roman Catholic Church to shape the educational development of Mexicans. During the presidency of Álvaro Obregón in the early 1920s, his Minister of Public Education José Vasconcelos implemented a massive expansion of access to public, secular education and expanded access to secular schooling in rural areas. This work was built on and expanded in the administration of Plutarco Elías Calles by Moisés Sáenz. In the 1930s, the Mexican government under Lázaro Cárdenas mandated socialist education in Mexico and there was considerable push back from the Roman Catholic Church as an institution. Socialist education was repealed during the 1940s, with the administration of Manuel Ávila Camacho. A number of private universities have opened since the mid-twentieth century. The Mexican Teachers' Union (SNTE), founded in the late 1940s, has had tremendous national political power. The Mexican federal government has undertaken reforms to improve education in Mexico, which have been resisted by the SNTE.