Students still prefer to interact with the teacher

In general I have found the students tend to prefer interacting with the teacher rather each other,and when they do interact with each otheg they do it mostly in L1 and not the target languusge of the lesson.This is especially the case with my young learners and the adult young learner Advanced class. The only exceptions were the IELTS class where they were motivated as their goal wad the IELTS exam.In my present Upper Intermediate class in the first classes they were interacting all the time in English but in the last couple to a lesser degree perhaps the students didn't need to show their ability to speak English. I have noticed the same thing happening with the Elementary class perhaps after half way through the course the motivation and enthusiasm had decreased.