Mother tongue instruction generally refers to the use of the learners’ mother tongue as the medium of instruction. Additionally, it can refer to the mother tongue as a subject of instruction. It is considered to be an important component of quality education, particularly in the early years (UNESCO, 2003: 13).
To ensure that children acquire strong foundation skills in literacy and numeracy, schools need to teach the curriculum in a language children understand. Mother tongue based bilingual (or multilingual) education approaches, in which a child’s mother tongue is taught alongside the introduction of a second language, can improve performance in the second language as well as in other subjects (UNESCO, 2016: 3)
UNESCO. If you don’t understand, how can you learn? Global education monitoring report: policy paper 24, 2016.