There is more than one philosophy about teaching ESL.  However, if you need the student's L1 to explain a word or an activity, then you are trying to do something too difficult for them. The students really need to learn to use dictionaries, to negotiate meaning and to guess - itself not easy for some students. They also need to choose between these strategies sensibly. Asking the teacher or a classmate for a translation will block this process.\n\nHere are some links that may help you.  Good luck with your research.