I don’t know when you went to HS, and of course, your experiences are your experiences, but I suspect that MOST kids at the kinds of HSs that sent kids to ~top 50 universities were aware of the significance of the SAT at least as far back as the 1980s and probably much further back. And yes, there were training exercises and so on, available and presumably used. FWIW, I think Kaplan and Princeton Review and the like have roots at least as far back as the 1980s, if not earlier.
Re: APs - they were less widely taken back then, but again, it was possible to study for them. I took 4 APs in the 80s without taking “AP classes”. At least one of them (Calc AB), I self-studied with a prep book for a day or two before the test.