The new preparatory school began functioning at the San Ildefonso building with more than 700 day students and 200 live-in students. The complex remained a separate entity until 1929, when the Universidad Nacional gained autonomy, meaning it became independent of the government, though still government-sponsored. The Preparatory School became part of the newly independent university system, being designated as Preparatory #1 for a short time. As part of the student revolts of 1968, some students hid inside the building, which resulted in an occupation by the Mexican Army, who entered the building by shooting a bazooka round on its 18th-century-old front door. Its name soon changed back to Escuela Nacional Preparatoria and remained so until 1978, when it closed completely.