Sorry icemaiden - been in a similar situation, my sons teacher last year was a waste of space and my elder son had had her the year before and she more or less tried to convince us that he had a learning problem - she referered him to Speak and Language therapy who came to the conclusion that he was bored as she wasn't challenging him enough. When my younger son was in the class - every report up to that point had been excellent all the way through - words such as "a pleasure to teach" cropped up. Went into her class and all of a sudden him and his group were all apparantly "not performing" anyway - ended up getting the head involved etc. at the end of the day, as you say, they all stick together and we got nowhere. by the time they finally replied he only had two months left of the year and was getting a different teacher next year so we didn't persue further. The Head Teacher attended the next parents night we had with her - I am not sure who she was there to check up on, us or her!
Anyway, good luck - might be worth asking the head to come along to the parents night and if possible write down some bullet points of your concerns and go through them methodically - if you don't get them all answered, hand them to the head and ask her to come back to you with a written response. Keep as calm as you can and avoid accusatory and inflammatory language if you can.
Let us know how you get on.