We were not allowed to have graphing calculators in elementary or highschool (90s), either.

I was in school around that time and I always had a graphing calculator in class and most of the time in standardized tests, AP tests, etc. It was basically just math competitions that wouldn't allow it. The graphing functionality was almost never used for anything. But the multi-line display could be used for notes, which is why they were banned for competitions.