Oh mazza, how infuriating! It looks like the mean spirited schools have been coming out of the woodwork the closer to Jan 15th we get (the more evidence they gatehr on the DCs, the more negative they seem to become!). It really does illustrate there is no consistency re predicted grades across school, and even more so with the loss of AS.
Is it by any chance the MFL teacher who is being especially pessimisitic?
When you say they won't change grades have you yourself raised it or just DD? Unfortunately, it seems this sort of thing is not really taken seriously until parents intervene.
Most teachers have not themselves had DCs going through the UCAS process and, therefore, don't understand at all how stressful it is , what a drain on time and resources Open Days are, and how early they might need to communicate PGs to students so that they can make realisitc choices/ negotaite grades.
Hopefully, you will get it sorted. Someone with all As and A*s at GCSE would be a failure on the part fo the school if they really did go on to get Cs and Ds at A Level!