英语教师如何在课堂上恰当的说母语

让学生用英语问
刚开始的时候说一下
后来就在板上写一些他们可能不懂的词(带含义)

At first, it is better if you ask them to ask in English, as they grow better, you can write down some vocabulary which they might don't understand and write down the meaning. Speak as less Chinese as the teacher can.