I am curious about something and wonder if you folks might offer some perspective. When considering acceleration, one of the things I've seen online and in some of the area school district documentation is demonstration of being "two years ahead" of peers. Why is it two years?

If child is in 1st grade, and showing strong 3rd grade achievement, then wouldn't you need to accelerate two grades, into 4th? Seems odd that you'd then do one year acceleration. Wouldn't one year solidly ahead be sufficient to consider promotion? Shouldn't the evaluation be for how quickly they learn? Is that just too difficult to assess properly?

It's fairly easy to show that the child is reading & comprehending 2-3 years ahead of grade, but isn't it possible that math, where the rules and methods might not have been exposed/taught yet, might trip up a child doing an above-grade-level assessment?

I guess it confuses me that innate ability and a need for a faster pace doesn't seem to be the primary indicator of acceleration, so it seems to require pre-teaching a high ability learner, which isn't the point, and then they're bored with redundancy yet again.

But maybe when you use the IAS the above is moot, as the scale weighs more factors than just that. I just don't get the reason for the apparent prerequisite.