The South African Language-in-Education Policy (LiEP) states that mother tongue should be the preferred medium of instruction in the Foundation Phase (grade R-3). Primary tuition is therefore currently offered in the 11 South African official languages. The challenge faced in South African schools that offer African languages in the Foundation Phase, is the fact that from grade 4 onwards, education is only available through the medium of English. This results in a vast number of learners having to make a transition in grade 4 to English as medium of instruction. In this qualitative study, I explored the experiences of teachers and learners in this transition. The context of this case study is a poverty-stricken and underdeveloped rural area. SiSwati is the language commonly spoken in this area and English is spoken, heard and read only in the classroom. Purposive sampling was done, including three grade 3 classes and their teachers, as well as the grade 4 learners and the teachers teaching siSwati, English and Mathematics. Data was collected through interviews, observations, document analysis and field notes. Conventional content analysis was conducted. Among the theoretical lenses adopted for the study was Krashen’s input-interaction-output model of second language learning. This informed the process grade 4 learners undergo in learning English as a second language and medium of instruction. The findings of this study revealed that the challenge regarding this transition is not the English language per se, but rather a deficient home language foundation and the quality of teaching offered. The learners’ age at the time of this transition also plays a significant role, as it affects their readiness to switch to another language. The implications of this study relate to the necessity of a solid mother tongue foundation and improved quality of teaching. It is suggested that the admission age in grade 1 be seven years and the actual point of transition prolonged.