I have noticed that the father of a girl in my Year 1 class is looking unkempt, has half-closed eyes and hardly speaks. This situation has developed over about six months so that I am becoming increasingly concerned when he comes to collect the child at the end of the day. I have mentioned this to the key stage co-ordinator but nothing seems to have happened. This situation is not usual for our parents.
On the surface, it looks as though the parent has a drugs problem, but one cannot jump to conclusions without knowing all the facts. There may be a medical condition that you are unaware of or he could be under enormous stress. It is not your role to take sole responsibility for the inquiry. You must bring your concerns to the headteacher and let the co-ordinator knw that you are still worried. The head can then see the parent and take any steps necessary to arrange support for the family.
However, if your relationship with the parent was good in the past then ask to speak to him about his child's progress. Judge whether the tone of the conversation is conducive to your mentioning how he looks changed and how you are concerned for his and his child's wellbeing. He may find it too difficult to talk about his problems so don't push. But more than likely he will want to share some things with you.
Let him know that the school is there to help him get the support he needs but that your main concern is his daughter's happiness and progress at school. If you handle this well, you may help the parent come through his difficulties and your pupil will be all right, but be prepared for this to be a long journey.