The purpose of this research was to investigate issues of both home language (isiXhosa) and the language of learning and teaching, i.e. English, when 9th grade second language learners engage in problem- solving and sense-making of real wor(l)d problems in multilingual mathematics classrooms. In addition, the study also explored whether the introduction of discussion and argumentation techniques in these classrooms can ameliorate these issues. The study used a pre-test – intervention – post-test mixed method design utilising both quantitative and qualitative data. The data collection strategies included interviews, classroom observations, and testing in four experimental and two comparison schools in townships around Port Elizabeth. Data analysis suggest that interventional strategy significantly improved the experimental learners'' problem-solving skills and sense-making abilities in both English and isiXhosa (but more significantly in English), and that introduction of discussion and argumentation techniques in the teaching and learning of mathematics word problems had a positive effect on learners'' ability to consider reality during word problem-solving.