How many homeschool students were tested in that group that were using homeschooling as a dodge of mandatory attendance laws and never completed their high school diploma?
Self-selection bias.
Tell us. Funny how I couldn’t find any study showing public schools outperform homeschools.
Do you want a valid comparison? Test all homeschool students and compare the results against the public and private school students who are also required to take the tests. Otherwise, there is no valid comparison because of the inconsistent data that is being used.
As I said, homeschooled students SHOULD be getting better scores. Unfortunately you method of trying to do that is flawed.
My two biggest concerns about homeschooling were the use of home schooling to dodge mandatory attendance laws, and the parents who fail at homeschool and then dump their kids back into public school after missing years of any quality education. Teachers are forced to make up for that time in addition to all of their other duties. I have seen far too many cases of each, up close and personally!