Purpose: The paper reports how lesson study helped to make the learning of students with limited English competencies visible in "Content and Language Integrated Learning" (CLIL). Design/methodology/approach: The two lesson study cycles took place in a Swiss primary school with a focus on three case pupils each with heterogeneous attainment levels in English. The research group observed how the case pupils coped with learning English integrated with art, crafts, and sports in four research lessons. Following a case study methodology, the research focussed on how the case pupils used their limited English language competencies complemented with multilingual and multimodal means to make their learning visible. Findings: Thanks to the close observations of students' learning and the detailed analysis thereof as a cooperative effort of the research group, the lesson study revealed that the case pupils used varied means to express their learning partly depending on their levels of English. Research limitations/implications: This small-scale case study only describes data collected from four research lessons based on a total of 12 case pupils. Originality/value: Commonly during lesson study, the students' learning is captured through the verbal language they use. But if the research lesson takes place in a foreign language setting in which students' language competencies are limited in expressing their learning, other languages and modes of communication must be considered. To date, there are few papers on how lesson study helps to explore learners' use of so-called translanguaging and trans-semiotising.