Reading comprehension is a fundamental resource for educational and social development. It is a skill that brings into play a diverse and complex set of processes and cognitive functions based on building a mental representation of a given text. We set out to study how different domain-general and linguistic abilities explain text comprehension in a population of secondary school students with low educational opportunities. The sample consisted of 45 adolescents between the ages of 13 and 15 from two secondary schools in the Province of Buenos Aires, Argentina. Each participant was evaluated both in-group and individually for three sessions during school hours. A text comprehension screening test and a battery of tasks that measure different underlying cognitive processes were administered. Using multiple linear regression, we found that vocabulary, non-word reading, and verbal inhibition are the skills that best explain reading comprehension skills. Understanding how much different domain-general and linguistic subprocesses are associated with text comprehension is key to designing effective interventions that are also grounded in theory.