In this article, I note an observable social turn in languages arts curricula in Latin America. However, I argue that the effort to contextualize written language and bring everyday uses of writing into the classroom falls short of promoting a critical understanding of some key aspects of how literacies work. To do this, I analyze a recent incident relating to the validity of some official documents used to receive the COVID-19 vaccine in Mexico City. Using a New Literacy Studies framework, I argue that official documents operate in local and practical contexts where local employees have a fundamental role in their validation. I show how the legitimacy of documents is continuously ratified or challenged in the contexts of use. Their validity is subject to interpretation, power dynamics, and social and cultural context grounded in local practices. I conclude that this has important implications for teaching and learning about literacy in school.