School didn't care about calculators, though they got wise to the fact that a programmable calculator could be used to carry arbitrary information into exams about halfway through my A-levels, at which point they mandated that any brought into the exam hall would have to be hard-reset in front of an invigilator. I recall buying a bag of 2.5mm jack plugs from Maplin (back in the days that they were good) and making up some Casio crossover cables at a fraction of the price of the official ones, so people could copy programs to each other's calculators and avoid losing them. There was a brief games/demo scene amongst the higher maths and physics sets.
Brizzle University (or at least the engineering faculty) had a list of authorised models, and I promptly invested in the most functional model on the list. (The only real benefits over a typical scientific model were a one-line edit history, which was a useful error-check, and numerical integration, which was much less useful than it sounds.)
I vaguely recall that UKC issued all first years CS student with their exam-legal model which they bought in bulk at a hefty discount. I didn't get one, as I went straight into the second year, but the Brizzle one was fine.
My CFX9850 has barely been used since uni. I've probably dusted it off a couple of times as a convenient out-of-band way of converting between binary, decimal and hex, but I've forgotten how to do anything clever with it.