One to four years of instruction in the local tongue has not shown to be sufficient because children in developing countries or poor communities generally do not have the capacity to switch from their L1 by the end of grade 3 and be simultaneously proficient in the curriculum. A study of South African grade 6 students who were educated through an L1 medium on average received a national achievement score of 69%, whereas those who were educated with an L2 achieved only 32%.
