Try and clarify for yourself the following before your meeting:
- what is the purpose of the meeting
- what do you want the meeting to achieve
Try and avoid a circular, repetitive conversation of 'we had an assessment which says DD is capable of achieving X, whilst you continue to insist DD is capable of only Y'. This will not get you anywhere.
Whilst you may disagree with the teachers assessment of your DDs achievement in school and feel hostile towards her, there is clearly a reason for the huge gap between home and school performance. Your concern clearly is that this gap is bigger than the normal difference which most children would display (home being more comfortable, involved parents giving 1-1 attention, less distractions etc.) and you want/need to try to establish the cause of the discrepancy.
This issue, which seems to be at the heart of your concerns, has little if anything to do with the ed. psych assessment you have had done and your DDs potential to excel in school. It has nothing to do with whether or not you like the teacher, although clearly you do not.
I feel you need to approach the meeting with a more positive attitude (which I know may well be very hard with the past history). You need to direct and use the meeting as an opportunity to identify what your DD is struggling with at school. My DD (in Reception) can do Maths at home at a much higher level than in school - she would fly through the year 2 and 3 curriculum if I let her. However she has not secured some of the basic, automatic processes she needs to (like number bonds) and I do not get unduly wound up when the teacher says she can do X and I know at home she can do much more because I do not feel it matters too much at this age. What matters is she secures the basic skills. If your daughter does not show security in basics at school then the teacher is, I feel, correct to focus on these. I appreciate you may not agree with that but it would seem pointless to me to extend her without having the fundamentals in place.
What would be more of an issue is why - when she is a very able little girl - she is struggling to secure this knowledge and demonstrate it consistently. This should be at the heart of your discussion with the school. The fact that she is gifted means she will learn/absorb new information quickly and with ease. It means she can understand complex issues, possibly well before her peers. It does not necessarily mean she has a good memory however and it may be that for some reason she is not able to retain some of the information she has previously learned. For this reason it may be wise educationally to slow down her rate of progress in maths and focus on fun ways of doing the necessary repetition to secure the knowledge she is struggling with. As I said my DD is assessed as being in the top such-and-such percent in Maths. She also has a problem with visual memory which means there are some aspects of Maths and reading she may actually struggle with despite her giftedness. Her giftedness may mean she excels in maths or it may mean she has the ability to compensate for the VM discrepancy and perform at an average/slightly above average level. Or it may mean that as she progresses through school she performs well below her potential. Only time will tell although I am hopeful that the work she does with the ed. psych will help her compensate for the VM deficit successfully. Being assessed as gifted does not necessarily mean outstanding performance is a natural progression. When you had the assessment done on your DD did you simply have tests done which measured her IQ or did they do a full educational assessment which could pick up potential learning difficulties?
If your DD is having a crisis of confidence and feels the teacher has no faith in her I would broach this with the teacher in a tactful way by talking about the fact you feel your daughter is losing her confidence in maths and you worry the anxiety is making her more error prone. Children like their teachers and want their teachers to like them and be pleased with them. I know you have posted before that you feel your DD has little desire to please the teacher but it is very possible that she is picking up on your own negative attitude towards the teacher and feels conflicted: in pleasing/liking the teacher she may feel she will displease you. If she is aware that you feel she should be doing more 'difficult' maths at school then she may be worried about disappointing you, more stressed and therefore more error prone.