This paper reports the interim findings of a longitudinal study which aims at exploring the effectiveness of a 3-year English Enrichment Programme, on top of the regular English curriculum, in exposing secondary students to more subject-specific English while they learn their content subjects in the mother tongue. The study was carried out in response to the Hong Kong government's decision to firmly promote mother tongue teaching in her post-colonial era after 1997. To evaluate the effectiveness of this programme on students' learning of English, in-depth study with selected schools was done and different research tools including questionnaires, lesson observations, interviews and language proficiency tests were used to collect both qualitative and quantitative data. It is found that the increased exposure to English may have had a positive effect upon students' perception of learning English, if not on actual performance. A closer look at the cases, however sheds light upon the intricate interplay between factors leading to the different degrees of perception about the effectiveness of the programme. These factors include: the willingness of the school to pool resources and efforts in making the most of the programme, the language competence of students, and the teaching focus and methods in class. Recommendations on the way forward will be discussed.