This study is part of an ongoing investigation of the knowledge base, learning and performance of Teaching English as a Second Language (TESL) students in the Canadian province of Quebec. The goal of the broad research initiative is to identify valid and reliable criteria for candidate selection and to provide those who are admitted to a programme of study with appropriate and timely academic support. The aim of the specific phase of the project reported here was to look at correlations between different forms of linguistic and metalinguistic knowledge and the academic performance and progress of two different groups of TESL students, the first enrolled in a grammar course and the second in a methodology course. The results reveal that the participants' scores on a metacognitive grammatical explanation task correlate strongly with their academic performance in the two courses considered, even when the course in question had no grammatical component. Vocabulary profiles in both French, the mother tongue of almost all the participants, and English were also found to correlate significantly with academic results in both classes, but to a lesser extent than the grammatical explanation task results. The assessment of the participants' progress over time reserved one of the biggest surprises of this study, with both groups of students showing significant improvement even though one of the groups had no grammatical instruction in the ten-week period of the study. (Contains 9 tables and 10 notes.)