Abstract
Prior knowledge and language of learning and teaching play a critical role in educational instruction. Prior knowledge offers a basis for learning, building onto the knowledge that learners already possess. Most South African learners learn using a home language that is an African language for the first four years of schooling, and from Grade 4 onwards, most learners switch to learning English. This study endeavoured to find out how Grade 4 teachers in bilingual schools teach pollution and the solar system in English to learners with Sepedi prior knowledge and how they use language effectively to equip these learners. The study used translanguaging and constructivist theory as lenses that underpinned the study. A qualitative approach was used, and data were collected by observing and interviewing five Life Skills and five Natural Science and Technology teachers from five schools. Three important findings were revealed by the study. Firstly, teachers prefer using English, as they are aware that sound knowledge of English has become indispensable for effective learning, especially since learners display an inadequate command of it. In addition, the use of the home language during lessons was not systematic enough to help learners understand concepts better, as it was sporadic rather than planned. Secondly, teachers’ input largely incorporated questions directed at learners, which might have been precipitated by their knowledge of the purpose of the study, and thirdly, most teachers did not use specific teaching or learning materials during lessons. The conclusion drawn from the study is that teachers largely used English to teach because of policy prescriptions, availability of materials as well as assessment requirements for learners to write in the language.