Due to the detrimental effects of apartheid on the South African learning environment the implementation of language policies aimed at fostering multilingual and multicultural education to attain educational equity are rendered impractical (DoE, 1995; de Wet, 2002; Pretorius, 2002b). As a result many L2 learners in English medium schools are struggling to reach their academic potential due to their lack of cognitive academic English language proficiency. This study aimed to analyse the effects of L1 and L2 reading ability for high school learners who were exposed to a reading intervention over a two year period, compared with those who did not experience the intervention. Performance on measures of comprehension and vocabulary over time were analysed regarding the gap in reading ability between L1 and L2 learners. Reasons for the results, limitations to the study, recommendations for future research, and implications for the South African learning context are discussed.