Definitely advocate for your child but, if at all possible, try not to be too confrontational. Go into the meeting prepared but with an open mind and be sure to really listen to what is being said. It never helps to antagonize the other people in the meeting. Get them on your side and you'll have more success. The child study professionals work very hard to try and help the children while dealing with an incredible number of legalities.
I agree with you--that mastering reading is the key to understanding other subjects. At the same time, I feel sorry for the teacher who is under incredible pressure to make sure all of her students do well!! I substitute teach frequently in elementary schools. It is absolutely incredible how disjointed some days can be for the teacher. Children are pulled out for special ed., for speech, and OT among other things--and at different times on different days. Add to that children who are sick or children whose parents pull them out for vacations. It is almost impossible--even for the best teacher--to remember which students did or did not learn something. Frustrating is an excellent way to put it.
Stay calm!! Good Luck to you. I hope all works out well!