This article documents the efforts by Mexican Americans to challenge school segregation in Arizona in the first half of the twentieth century. As in Texas and California, although state law never formally mandated the segregation of Mexican American students, school districts in Arizona often established separate "Mexican Schools" for Mexican American students. While districts argued that segregation was necessary because of students' poor English skills, the segregation of Mexican American students in Arizona's public schools was not an isolated practice but occurred in tandem with other discriminatory practices that restricted the social rights of Mexican Americans, many of whom were American citizens. However, Mexican Americans challenged segregation in the courts. Notably, in "Gonzales v. Sheely", a case heard in the United States District Court of Arizona in 1950, Judge Dave Ling declared segregation unconstitutional over three years before the Supreme Court's historic decision in "Brown v. Board" (1954). (Contains 8 notes.)