My wife didn't end up taking the SAT or ACT because she attended a relatively strong local university with a full-ride scholarship and a test-optional policy. The MCAT exam initially denied her request for accommodations because she was only diagnosed with a learning disability in college. We successfully appealed by writing an essay arguing that my wife wasn't diagnosed with a learning disability in K-12 because her schools sucked (we submitted documentation that proved that her schools tested among the worst in the state, her elementary school was literally the worst in the entire state, when she was a student), and her teachers had much bigger concerns than why the smart, studious kid takes a long time to complete exams.
If the wife had gone to the K-12 school system that I attended, her learning disability would have been addressed in elementary school, and she would have been spared much angst. I was a very poor reader in early elementary school, and received almost daily one-on-one attention at my school from instructional aides and volunteers (mostly highly educated parents and grandparents) for years. I received a perfect score on the ACT reading section in high school.