In a longitudinal design, we measured 50 low-achieving adolescents’ reading comprehension development from Grades 7 to 9. There were 24 native Dutch and 26 language minority students. In addition, we assessed the roles of (a) linguistic knowledge, (b) metacognitive knowledge, and (c) reading fluency in predicting both the level and growth of reading comprehension. Students improved in reading comprehension, the language minority students more so than the native Dutch students. We can explain the level of reading comprehension by linguistic and metacognitive knowledge, whereas most fluency-related predictors appeared to be of minor importance. We can hardly explain the growth in reading comprehension by the predictors. Nevertheless, we found a significant interaction indicating that growth in vocabulary explained growth in reading comprehension for the language minority students. This finding seems to suggest that language minority students profit from gains in vocabulary, more so than native students.