Students learn more with their mother tongue as the medium of instruction than the use of English alone.

because: students' first language serves as a mediating device to understand particular linguistic forms among learners sharing the same first language (Anton (1998) )
but: the maximal amount of target language should be used in a foreign language classroom (Turnbull (2001) )
- but: language learning does not happen when students receive inputs exceeding their cognitive capacities (Krashen (1981) )
  - but: target language inputs can be made comprehensible by adjusting them to the students' level of proficiency (Bae (2008) )
- because: the amount of the target language use is positively related to target language gains (Cummins (1986) )
- because: students spend only short periods of time in class on a daily basis and have little contact with the target language outside class
because: when the concepts learned are too difficult or take too much time to process, the learners' first language may be used (Cook (2001) )
- because: 1
because: students who were given science lessons in English had a more limited learning experience than those who were taught in their mother tongue (Yip (2007) )
- because: 2
because: using ESL students' first language (L1) in class improves learners' self-image and motivation (Balosa (2006) )
- because: 1
because: teaching in the students' mother tongue leads to better cognitive development
- because: students will be able to better understand what is taught, analyse problems, express views, develop an enquiring mind and cultivate critical thinking (Education Department (1997) )

Anton, M., & DiCamilla, F. (1998). "Socio-cognitive functions of L1 collaborative interaction in the L2 classroom." Canadian Modern Language Review, 54(3), 314-342.

Bae, G., & Kim, E. (2008). "What causes reliance on English? Challenges and instructional suggestions in a drive for using a target language only." Applied Language Learning, Vol. 18, Nos. 1 & 2, pp. 63-76.

Balosa, D. "Three examples of better English learning through the L1." in Essential Teacher, Vol. 3, Issue 1, Mar. 2006. (http://www.tesol.org/s_tesol/secetdoc.asp?TrackID=&SID=1&DID=5720&CID=1222&VID=213&RTID=0&CIDQS=&Taxonomy=False&specialSearch=False)

Cook, V. (2001). "Using first language in the classroom." Canadian Modern Language Review, 57, 402-423.

Education Department. (1997). Medium of instruction guidance for secondary schools. Hong Kong: Printing Department.

Krashen, S. (1981). Second language acquisition and second language learning. Oxford: Pergamon Press.

Turnbull, M. (2001). "There is a role for the L1 in second and foreign language teaching, but..."Canadian Modern Language Review, 57, 531-540.

Yip, D.Y., Coyle, D., & Tsang, W.K. (2007). "Evaluation of the effects of the medium of instruction on science learning of Hong Kong secondary students: Instructional activities in science lessons." in Education Journal, Vol. 35, No. 2. The Chinese Univ. Press.