I'd suggest that you keep smiling, and try to get a written agreement regarding how long the trial will be, and what the criteria will be for continuing or not.

If the school doesn't come up with a doc, you can. You can take notes at the next meeting, write them, up, and say, "Thank you for the meeting. I'm so pleased that you share my concern about finding the best placement for dc's social, emotional, and academic well being. My understanding is that we will have a six week trial..."

good luck!