This opinion piece dates SHSAT test prep to the 1950s. Of course, the entrance exam was not called “SHSAT” back then, and there was one exam per school.
When I was an 8th grade student in the 1957-58 school year at George Gershwin JHS, a jewel of a school recently opened on Linden Blvd in East NY section of Brooklyn, male students were offered an opportunity to take an after school class in prepping for the test for Brooklyn Tech, at the time the only specialized high school that went from 9th-12th grade. The others, Stuyvesant and Bronx Science began in the 10th grade and for those schools the test was taken in the 9th grade.
Norm Scott
Now I should point out that at Jefferson I was among an elite group of about 200 students who were in “honor school”, a sub-school of college bound, and over the next three years we received what I considered a college-level education. But Jefferson also wanted to compete for elite status and considered gaining a NY State scholarship a measure of success. Thus we were pulled from gym cycles over the next year and a half to prep us for that test.
Norm Scott
The point is that schools were offering test prep as far back as the 50s but it was free to all students who were deemed as having potential.
https://ednotesonline.blogspot.com/2019/08/the-wave-school-scope-those-shsat-tests.html