English perfectly shows the "network effects" of a global tongue: the more people use it, the more useful it is. Parents expect their children (master)English, which is encouraging the (grow)of private schooling. Education authorities are switching to English medium, in part to control the outflow(外流) of children into the private sector.
Teaching children in English is fine if that is they speak at home and their parents are fluent it. But that is not case in most public and low-cost private schools. Children are taught in a language they don't understand by teachers English is poor. The children learn neither English nor anything else.
Research shows that children learn (much)when they are taught in their mother tongue than they do when they are taught in any other language. In a study of children in 12 schools in Cameroon last month, those taught in Kom (do)better than those taught in English in all subjects.
English should be an important subject at school, but not (necessary)the language of instruction. Rather than switching to English-medium teaching, governments fearful of (lose) custom (光顾) to the private sector should look at the many possible ways of improving public schools.
