The English teaching faculty at the authors' institution contains a wide range of teachers with varying ability and inclination to use Chinese in the classroom. Teachers and students alike differ on whether explanations should be offered in the mother tongue, and to what degree. The authors surveyed 708 students across 15 language lab sections in an effort to determine whether classroom language policy matters, and if so, what the direction of its influence should be. We found a preponderance of subjective student support for bilingual instruction, but very little evidence that it makes a positive contribution to graded student performance. In fact, the study found strong evidence that students' preference for mother-tongue explanation is associated with poor grade performance, but the students expressing this preference included both those not getting any L1 instruction and those at risk of becoming too dependent upon it. Examination on of individual teachers and classes did reveal a significant association between pure monolingual instruction and low grades, but also suggested that this could be due as much to correlated traits like overall pedagogic strictness as to language policy per se. Exactly what other teaching traits are most closely correlated with monolingual instruction, and how they influence student learning provides an interesting venue for further research.
