You may be teaching a group of learners who has differing abilities of English in the same classroom. If this is the case, then don't worry. The best you can do is to assign roles and different activities for each individual learner. If you have a student who finishes an activity early, then get that person to help the slower learners in class.
Don't worry and try to think of practical ideas which you could do to improve all learners in the class and always have some extra material for stronger learners to complete while you all wait for the lower level learners.