When I took the test in 1957(using clay tablets and cuniform chisels)the ONLY students encouraged to apply for the limited seating were members of the honor society whose grades and academic attitude were deemed worthy. The rest of the students at this very highly rated school simply didn't take the test at all. I suspect that students are taking the test today who would have been channeled into auto shop or steno school in my day.
One further note. I wasn't in the honor society, not because of grades, but because I had some "u's" on my record for "Unsatisfactory deportment". Therefore, I wasn't even told about the test. It took a caring and active home-room advisor to circumvent the rules and get me into the test. (My innate modesty prevents me from posting my scores--but I was able to choose between scholarships from Harvard and Columbia. Roar Lion, Roar.)
There are students taking the test today who would not have been in your class in your day. They would have been held back for one or two years. Not to knock those students in your day. Some of them probably took the SAT one or two years later, and did OK. The extra years, and the extra attention may have paid off.
By the same token, there were probably more kids who were promoted one or two grades in your time, also. The Leveling out of standards have leveled our kids at the same time.
That depends. In Michigan, very few students take the SAT because colleges in the midwest rely mostly on the ACT. As a result, not even all honor students take the SAT.