I don't remember. I just remember having a discussion about it, maybe even a TMEA clinic in the early 2000's. I came from a place where beginners started in 4th grade and couldn't believe my beginners in Texas didn't start until 6th or 7th grade and then stumbled on that info.

And in my own teaching I had 7th grade beginners over the years that in 9th grade were making the Varsity, NV, and SNV bands at a 6A high school. Best kid I ever started as a 7th grader was varsity Middle school in 8th grade and All region for 4 years in high school.

I wish I had the study but I don't.