Dr. Yell helps us to define "progress" as it has been described after Endrew F. v. Douglas County Schools (2017). Here's an article he wrote: https://drive.google.com/file/d/1Fa_ZgzItiGYJ0AMqRSy-MGBE_TzfuXJr/view?usp=sharing
Here are some books he wrote: https://a.co/d/8iKAo8J
https://a.co/d/8kBIyMd