Just want to add some support to including the psychologist in the meeting. I say this not just as a psychologist myself, but from my own experience with my kids when they were going through this. It adds some authority when administrators, teachers, etc. start "debating" the merits of various scores, and you have someone there who is actually trained and can point out inaccuracies in their arguments.
I had a situation with one of my kids a long time ago, where he was almost excluded from a gifted pull-out because of the GT teacher's misinterpretation of scores and inability to integrate information in a meaningful way. The school psychologist tactfully but forcefully let her know she was completely out of line.
Good luck.