Ooh dear. Poor her and poor you. My first thoughts are as follows. Others may well disagree.
disenchanted wrote:
My dd is in Yr 12 at a selective school in London...the school have suggested it may be better for her to study at a college where she is better supported and does regular tests.
I need to ask, is this a fee-paying school? It is almost unheard of for a school to make 'suggestions' of this kind and it feels very harsh of a school to do this to someone with a recognised learning disability who has been at the school since Y3. But if it is a fee-paying school you may have little choice but to follow their 'advice'. It is something of an indictment of their own teaching if they feel 'a college' is able to support your daughter better and offer her the regular tests they feel she needs - why can't they do it? If it is a state school they will be obliged to do so, but a private school has no such commitment sadly.
disenchanted wrote:
My worry is that if she continues to perform erratically in exams, her A-level predictions will be poor and she will not be able to go to University.
This is one of the things about education, I am afraid. There is no real answer to that - any number of factors will be affecting your daughter, not least now the uncertainty around which school she is going to go to in September.
disenchanted wrote:
She is very unwilling to defer entry.
Why? Why not think about a gap year? It would take the pressure off her and allow her to apply to places with her grades already. 2 of my 3 children did this with huge success and the third, who is the same school year as your daughter, is going to do the same. She is still young and it sounds as though she has enough to deal with right now without worrying about university courses. One step at a time - sort the school out first.
I feel for you as it looks to me as if she is being let down by her school at a very crucial stage in her education. I imagine they are worried that poor results will reflect badly on them in league tables

. The first port of call has to be the school, but in this case I think it does depend on what type of school it is. Good luck.