In addition to disability issues you point out, I would expect that there was also a very strong racial/class correlation with that section. I'm from a middle class white family and my parents both went to college and speak "proper" english with minimal slang. I didn't study at all the for the grammar section and just chose the option that sounded right to me and I aced it. I'm sure it was more difficult for people from communities that speak different dialects/vernacular.
https://blog.prepscholar.com/sat-score-chart-raw-score-conve...
1. Take the test the year before they added the essay, so you'd have the "non-essay" exam grade recorded. Even if you were in 9th or 10th grade, that's still useful.
2. Take the test again with the essay. But when you do so, have AP classes worth of "knowing how to write against a graded rubric" experience so that you beat everyone else's writing score. (Thank you AP World History teacher that I've forgotten... I'm pretty sure she taught me how to beat an essay portion on any test)
My entire college-bound peer group took the SAT twice, once without the essay and once with the essay. Literally all of us, every single friend/acquaintance in my year. Most of us took the PSAT (practice SAT) to get used to the "timing" of multiple choice. (When you're low on time, its time to start guessing and moving way quicker)
The exceptions were the military dudes, who left for the Iraq / Afghanistan wars. So they had no need to take the SATs.
We all were worried about how the essay would be graded, whether or not colleges would accept the essay score, or whatever. Some of us even took alternative tests (ACT) in addition to the SAT (I only took the SAT twice).
For us, the essay thing was announced long-in-advance and we literally strategized our college acceptance plans around it. I don't know who figured out the essay announcement, but... it was very well known in my bubble.