The IAS has nothing to do with gifted ID - it is specifically to determine whether a child should do a full grade skip. I think under the circumstances it would be worthwhile to jump online (
http://www.accelerationinstitute.org/Resources/IAS.aspx)
and purchase one (
http://www.amazon.com/Iowa-Acceleration-Scale-Manual-3rd/dp/0910707928) (cheaper on Amazon - you may even be able to get a used one, which isn't a problem). Do the scale ahead of time and use very conservative estimates, and see what you get.
How you handle this in the meeting is challenging. You might want to say something along the lines of "I must have completely misunderstood what you said, because I thought you said you used the IAS for gifted ID, and of course that couldn't be right. But since I wasn't sure I bought a copy and you know, it definitely supports acceleration in our case." Don't back them into a corner, unless completely necessary, because when people feel threatened, they tend to not listen.
Someone else posted that you should make it absolutely clear that you take responsiblity if the skip doesn't work - they will want to be sure you won't come back and blame them if things go bad (it won't - if the IAS says to go forward, you will be fine).
Cat
