Tip: When your pre-experience students are working in groups, give them a follow-on task that forces them to listen and get involved.
This idea was suggested to me by a student (now in-work) when I asked him to reflect on his pre-experience days of learning English with their usual problems of mixed ability, students reverting to mother tongue etc. As preparation for this website, I asked him for his one best tip to teachers for how to cope with this situation.
He said that it is very important to give a follow-on task with groupwork, announced clearly before the first task begins. For example, if it is a discussion or meetings role-play in small groups, then tell the students that you will regroup them afterwards for them to tell a new partner what they discussed. Or tell them that one of them will have to present their ideas/conclusions to the whole class. Or tell them that for homework they will have to write an email to a (imaginary) colleague who wasn’t there to summarize what was discussed. Or that they will have to write a short report on the ideas presented in the meeting and the final outcome.
You get the idea. It just helps to keep everyone involved and on track. The students know that if they do go off-task they will not be able to complete the next task. It won’t always work of course, but it’s certainly worth bearing in mind.