Is it impossible that a teacher teach without using a indonesian language ?

            In my opinion, it’s impossible that English teacher  teach without using Indonesia language, because as an Indonesian people, English is a foreign language, so teaher must be mix between Indonesian and English language in teaching and learning process.  
If a teacher teaches in the English language continuously regardless of whether the student can understand the material or not, so the learning is not effective, because students will not be able to feedback and discussion with teachers about the material taught in that day.
So it,s effective and efficient when a teacher uses language that is mixed, between the source language and the target language in teaching and learning process.