When he was five years old, his family moved to Mexico City to provide a better education to their children, where Sánchez de Tagle was enrolled in a religious primary school run by the Bethlehem Fathers.

He studied Homer, Virgil, Descartes, and Leibniz and gained knowledge in mathematics, astronomy, physics, history, geography, and chronology.

[7] As the First Mexican Republic gave way to the Centralist Republic of Mexico, Sánchez de Tagle helped draft the Siete Leyes, giving a discourse to congress on establishing a fourth branch of government, which would eventually become the Supreme Moderating Power, a council that was constitutionally above even the president, and which Tagle would be chosen to be a member of.

[9] He also engaged in philanthropy, belonging to the junta of the charitable institution, the Hospicio de Pobres, and was president of the Lancasterian Company, whose purpose was to promote education in Mexico.

He was a devout Catholic who also advised theologians in Mexico City on difficult cases, and in 1831, the Vatican sent him a dispensation granting him permission to read all forbidden works.

[12] In 1836, he was named director of the Nacional Monte de Piedad, the national pawnshop, and he held his post during the Mexican American War.