Many native-speakers of English feel hesitant about correcting students' accents, for some reason. If we do enough remedial work at an early stage, it helps prevent situations such as the one you are in.
When students are at an advanced stage, it is often too late to help them a great deal, but do what you can in the classroom. You may feel that grammar and lexis are more important than pronunciation, but remember that errors in stress and pronunciation can impede understanding as much as those in grammar.
Those who are easily shocked should not read on.
A young lady who says, "Can you helps to me, please; I wants to know how is I get to the railway station" is unlikely to be misunderstood. However, if she says that all she want from life is /ə ˡpiːnIs/ when she should have said /ˡhŠpines/, she will be misunderstood, and cause some embarrassment to herself.
- For Teachers