One thing that sets Mr. Castro apart from the other presidential candidates is that he is currently the only Latino candidate. And although running for president is something only three other Latinos — Bill Richardson, Ted Cruz and Marco Rubio — can relate to, the policing of Mr. Castro’s language may well feel familiar to many Americans of Latino heritage.

I often see this difference in who gets praise for speaking Spanish play out in my job as a college Spanish instructor. Our language education model is geared toward teaching the O’Rourkes and Buttigiegs. We celebrate and promote the success of elite bilinguals, students whose first language is typically English. Teaching languages to monolinguals is perfectly fine; it is, mind you, how I make a living. It is refreshing to see politicians as positive role models for second-language learning.

In contrast, immigrants and people of color find themselves at the margins of language education as minoritized bilinguals. Instead of building on their multilingualism, our school systems place them in E.S.L. programs, often for longer than necessary. Language teachers share part of the blame. We have traditionally put more emphasis on correct verb endings than on the language practices of neighboring Spanish-speaking communities. When the Castros on our campuses enroll in a language class, they often end up in courses designed with Anglophone students in mind. Worse, when they take courses billed as language classes for heritage speakers, the instruction often belittles the Spanish spoken by Latinos in the United States as conversational, casual or even uneducated. This is an area where we need to do better.

To be sure, Mr. Castro himself has repeatedly stated that he does not speak Spanish fluently. He first addressed this issue when he rose to national prominence as the 35-year-old mayor of San Antonio, then again in his 2018 memoir, “An Unlikely Journey: Waking Up From My American Dream,” and in other media appearances. I have no trouble believing that he is sincere in his self-assessment because I have listened to many students with comparable life stories describe their proficiency in similarly negative terms.

In truth, terms like “fluent” and “bilingual” mean little because they are vague and subjective. When Latinos describe their Spanish as not fluent or not good enough, they have often internalized the idea that the Spanish spoken in, say, the West Side neighborhood of San Antonio is inferior to the Spanish spoken in Madrid, Bogotá, Colombia; or Puebla, Mexico. But to my ears, all varieties of Spanish are equally valid.