In the years following Texas' independence from Mexico in 1836, Mexican citizens were allowed to apply for Texas citizenship. By categorizing Mexicans as racially White, Texas could effectively restrict citizenship to Whites only and prevent freed African Americans from obtaining citizenship. However, due to insufficient documentation, many Mexican citizens were still denied status as Texans.
A century later, as segregationist policies were being publicly condemned in the United States, the existence of Mexican schools received far less national coverage as a result of being deceptively categorized as White schools.
In 1947, even after a high court found that separation "within one of the great races" was not permitted and segregation of Mexican American children, who were considered Caucasian, was illegal, such separation could be pedagogically justified by scientific language tests applied to all students.
In 1948, Mexican schools became illegal as a result of the ruling in Delgado vs. Bastrop ISD, but school policies continued to lean on such language tests to discriminate against Hispanic students. In the 1970s, several landmark lawsuits were aimed squarely at discriminatory enrollment practices carried out in the name of bilingual and dual-language education in the state of Texas.
Since these institutions weren't ever formally acknowledged at the time of their existence, little documentation of them exists; however, it is estimated that, during the 1940s, at least 122 school districts in Texas established Mexican schools.