I had a phone conversation with the teacher yesterday (at my request in lieu of not being able to get the appointment). The teacher is absolutely lovely.
She started by saying that he is a model pupil, very intelligent etc and that she had no concerns about him as he is in the top set and turning out work that is slightly above the midline of the class.
However, although she did know about DS's sen diagnosis, she wasn't aware of the impact it was having on pulling down his grades (because he's doing reasonably well anyway). Also, she wasn't aware that he's supposed to get extra time in exams.
I think she was genuinely shocked when she realised what she's missed, but when she looked through his work file and saw the evidence for herself, she did agree with me that what he knows is not making its way onto the paper.
Sometimes, information needs to flow in 2 directions, which is why I think its wrong to decide that, as teachers, you already have all the relevant facts and therefore don't need to speak to the parents.
Saying that, I do understand that you will be making a good call at least 90% of the time, and there is only 24 hours in a day. I am not criticising you, just pointing out that its a mistake to assume that you already know all that you need to.