Some of my teachers required you to use the school-owned calculators, which were cleared after every class. Other teachers specifically allowed you to use your own programs during class.

I think that it was pretty common for students to trade programs around, so most of the teachers knew that the calculators were programmable.

My high school precalc textbook actually walked you through the process of writing a simple quadratic formula solver program. By this time, I had actually already gotten into writing TI-BASIC (as the first time I really started learning to program, failing to wrap my head around both python and C before) and I had created a slightly more complicated formula program with input sanitization and error handling, as well as a few other silly formulas. After this chapter I started passing around this program, as well as a small game I had written. These things were probably the most recognized I will ever be for my code, and I still have both programs.

Exactly the same story here. I really enjoyed my time tinkering with the TI-84.

Yeah ! School was so boring, programming calc is what got me into computer science. I'll never forget all my programs for IFS fractals, Syracuse suite visualization, Tic Tac Toe, Minesweeper...