Welcome to the forum.
Sorry to hear that you're having some problems with the group. The problem with teaching adults (and some kids) is that if they don't want to work, they won't work. If they have no incentive, why should they?
Why are they taking IELTS?
I must make one important point, though. As their teacher, it is your responsibility to ensure that your own English is of a very high standard, preferably near-native. It is clear from the number of corrections I have had to make to your post above that that is not the case.

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