This paper, which is a part of a thesis, investigates the perception and practice of lecturers and students with regard to lecturer-student interaction in English medium science lectures of a university in Sri Lanka where English is a second language. This paper argues that dialogic lecturer-student interaction, which enables students to take a more active role in discussions compared to the use of recitation scripts (questions-answers-evaluations) developed in non-dialogic interactions, is likely to be beneficial for students' content (lecture comprehension) and language development. The study revealed the complexity of the perception-practice dynamic, and the multi-faceted sub-set of factors which influenced students' and lecturers' behaviour in class, and their perception of that behaviour. Students' lecture comprehension and classroom interaction were influenced by their language proficiency, though the students considered the lecturers' lecture delivery style to be more important than their own language proficiency. This study also revealed that a culturally-embedded behaviour perpetuated by senior students, known as ragging (a kind of bullying), restricted the classroom interaction of the students.