I didn't actually read the article- shame on me.
Agreed.
How are there measuring where kids actually are grade level wise?
Read the article.

You may also wish to read the related thread linked in the OP.
I have a piece of paper with the WJ -IV results on it that say my child is performing at a > 13 grade level almost across the board (except speed). But in real life what does that look like? Yes, he can read anything but he doesn't have the life experience to really understand high school literature. He wouldn't thrive in a high school literature class.
Math would be slightly different. He could work six years ahead, but his EF skills wouldn't keep up being placed there in and BM school.
Agreed.
1) The point which you raised, while valid, is a separate topic from the findings of the
study, which are summarized by the linked
article.
2) When contemplating accelerated grade placement, the Iowa Acceleration Scale (
IAS) is the go-to tool, and it considers many factors - not just the results of one achievement test.
3) The
article mentions, "
... uniformly positive benefits when academic acceleration is implemented thoughtfully."
I'm starting just now to realize that school teaches a lot more than just grade level content.
This seems related to the thread
what kids don't learn.