When I was in our high school equivalent, our maths teacher blew that trick out of the water simply by having us all clear the calculator memory, then having us swap calculators at random.
Worked a charm. Next time, noone had bothered to hide notes as they didn't want to spend time helping some random sod out.
Solidarity is dead.
(You could, of course, try to counter this by having the entire class install the same cheat - but that would be unlikely to succeed...)
Oh, we had one approved graphing calculator - well, two. The Casio FX-7700 and its big brother, the FX-9700.
Problem solved. Except if you happened to prefer RPN; I had a HP-48 which I had bought prior to the edict naming The One True Calculator - the day I enrolled at university, I started using it again, only to be met with a similar edict in my second term, naming the Ti-89 the only kosher graphing calculator.
Since I graduated, the HP-48 has been in daily use.
Worked a charm. Next time, noone had bothered to hide notes as they didn't want to spend time helping some random sod out.
Solidarity is dead.
(You could, of course, try to counter this by having the entire class install the same cheat - but that would be unlikely to succeed...)