In the Netherlands many adolescents struggle with text comprehension. They may lack the necessary linguistic or metacognitive resources or might have problems accessing these resources efficiently. This longitudinal study addressed (1) whether linguistic and metacognitive knowledge and processing speed predicted reading comprehension, (2) how reading comprehension developed over time, (3) whether growth in linguistic and metacognitive knowledge and processing predicted reading comprehension development, and (4) whether findings differed for bilinguals and monolinguals. A multi-level growth analysis was conducted on reading skills of 50 low achieving bilingual and monolingual students (grade 7-9) in and around Amsterdam. Several linguistic, metacognitive, and processing skills were assessed. Results indicate that both bilinguals and monolinguals improved in reading comprehension over the three year period. In addition, the bilinguals’ initial reading comprehension was lower than that of the monolinguals, but they improved, more than the monolinguals. Furthermore growth analysis showed that linguistic and metacognitive knowledge significantly predicted students’ reading proficiency. In addition, growth in reading comprehension was associated with growth in all measures of linguistic and metacognitive knowledge and processing efficiency. These results will be discussed in terms of their theoretical and practical/educational meaning.