A medium of instruction (plural: media of instruction, or mediums of instruction) is a language used in teaching. It may or may not be the official language of the country or territory. If the first language of students is different from the official language, it may be used as the medium of instruction for part or all of schooling. Bilingual education or multilingual education may involve the use of more than one language of instruction. UNESCO considers that "providing education in a child's mother tongue is indeed a critical issue". In post-secondary, university and special education settings, content may often be taught in a language that is not spoken in the students' homes. This is referred to as content based learning or content and language integrated learning (CLIL). In situations where the medium of instruction of academic disciplines is English when it is not the students' first language, the phenomenon is referred to as English-medium instruction (EMI). In different countries and regions Africa In Tanzania, Swahili is used in primary schools and adult education, whereas English is used in secondary schools and universities. In Zimbabwe, use of English, Shona and Ndebele is established in education until the fourth grade; from the fourth grade, English is the medium of instruction. In South Africa, students are taught primarily in their home language from Grade Zero (Reception Year) up to Grade 3. From Grade 4 onwards, English is the default language of learning and teaching, except for a minority of schools in which Afrikaans is used. The national curriculum requires that all students study at least two official languages as separate subjects, one of which must be studied at home language level and the other at least at first additional language level. The most common home language among the school population is isiZulu. In Nigeria, Medium of Instruction at all levels of education (primary, secondary, universities and colleges) is English Language. In the francophone states of Africa, education has typically been in French only. In Ethiopia, Amharic, Oromo, and other Ethiopian languages serve as the medium of instruction in primary education, while English is used in secondary schools and universities (French had been the medium of instruction in public schools pre-1936). Western Hemisphere Brazil Every public school uses Brazilian Portuguese as the medium of instruction, but no law prohibits the use of other languages in private schools. Many schools use other European languages