Student Number : 0302922V - MSc research report - School of Education - Faculty of Science / The difficulty of teaching and learning mathematics in a language that is not the learners' home language (e.g. English) is well documented. It can be argued that underachievement by South African learners in most rural schools is due to a lack of opportunity to participate in meaningful and challenging learning experience (sometimes due to lack of proficiency in English) rather than to a lack of ability or potential. This study investigated how improvement of learners' English language proficiency enables or constrains the development of mathematical proficiency. English Computer software was used as intervention to improve the English Language proficiency of 45 learners. Statistical methods were used to analyse the pre- and post-tests in order to compare these learners with learners from another class of 48. The classroom interaction in the mathematics class before and after the intervention was analysed in order to ascertain whether or not the mathematics interaction has been enabled or constrained. The findings of this study were that proficiency in the language of instruction (English) is an important index in mathematics proficiency, but improvement of learners' language proficiency, even though important for achievement in mathematics, may not be sufficient to impact on classroom interaction. The teacher's ability to draw on learner's linguistic resources is also of critical importance.