“Now”? It was referenced in Peanuts - when Linus was running for student council president, one of the things he pledged to get rid of was “kindergarten cap and gown graduations.” There was also a scene in a TV special where Sally is in a cap and gown, getting ready for one. (In print, after his last campaign speech mentioned The Great Pumpkin, the storyline ended; on TV, he ended up winning, but it ended with a closed-door meeting with the principal, who made it quite clear which one of them called the shots at the school.)
We had an 8th grade “promotion” ceremony (Texas, 1980s). “Graduation” was reserved for completing high school or college.
87 is “recent” to me, given that I was graduated from high school in 1985. I was promoted from kindergarten to the first grade when the Vietnam war was still raging.
I’m a few years older than you , and I was graduated from elementary school (8th grade) in 1977 and my public school friends were graduated from junior high (9th grade) in 1978. And I know I attended a kindergarten graduation sometime before 1978 , so graduating from anything before your senior year of high school is not all that new.
Those were the days when a great many high school students, upon completion of 12th grade, got “promoted” to “Private”. (Getting promoted to “Private First Class” took several additional weeks.)
“You’re in Love, Charlie Brown” from 1967 (Peanuts 1960's Collection DVD Review "Also, valedictorian Sally prepares for her cap-and-gown kindergarten graduation. ")