Thanks Jules726 and mnmom23 for your advice. It's really helpful!
I actually saw a few glimmers of hope from the school this week. The District TAG coordinator came to the elementary school and tested DS, just as she promised. I happened to meet her on Tuesday after she had just completed her second testing session with DS. Since DS was there, we didn't have an opportunity to really talk. But she did whisper on the side to me, "He's VERY smart!" And she has been teaching for over 20 years, so she has quite a bit of experience from which to draw. This gives me some hope that she might be a good advocate for us.
At this point, I'm going to wait for the school's test scores to come back and for a meeting with the District TAG coordinator and others. I'm hopeful that at that meeting, my request for acceleration will be better received!
But mnmom23, I like your ideas about the reading acceleration. I will try those out. Thanks!