Yah. It's weird that de Boer argues selection bias is in play in SAT participation between MS (3%) and CT (88%) when 100% of MS high schoolers take the ACT. That seems to be what's happening here: the kids in MS taking the SAT in addition to the ACT are the ones aiming for elite schools.
You say it better than I do. Agreed it's an extreme selection bias, just want to point out that it's slightly different than the one de Boer seemed to be pointing out.
It's still the same bias he argues, the three percent are the most motivated and prepared. Why the other 97% skip it isn't relevant in this argument, but the number is independently shocking without the context. I fell for it until the ND mention, and I took the ACT.
You seem to be taking issue with the fact that the piece could be interpreted as implying 97% of MS students didn’t want to go to college. Obviously, if that was his point, he was omitting the most important detail.
His point was that if you bias the data source, you get results that you shouldn’t project onto the general population. The specific explanation of the 97% disinterest in the SAT is well and truly irrelevant.
My issue was more the opposite. If the author is saying, hey, only 3% of kids take the SAT which creates selection bias, most people will immediately wonder why the low percentage. The ACT info adds support and explanation to his own argument, so it should have been included.
I'm from the East Coast and I took both, submitted both on college applications (I actually did slightly better on the ACT, not sure if it helped) but yeah SAT was given priority in school/training programs. I had to seek out the ACT.