And the "problem" that teachers would not know how your particular brand works sounds weird. There are so many ways to figure this out. I mean the student can read the manual. Or ask for help from fellow students.
And our standardized secondary school graduation exam defines what you can do with calculators:
> On solving the problems, you may use a calculator that cannot store and display textual information. You may also use any edition of the four-digit data tables. The use of any other electronic device or printed or written material is forbidden!
> The use of calculators in the reasoning behind a particular solution may be accepted without further mathematical explanation in case of the following operations: addition, subtraction, multiplication, division, calculating powers and roots, n!, n-choose-k, replacing the tables found in the 4-digit Data Booklet (sin, cos, tan, log, and their inverse functions), approximate values of the numbers π and e, finding the solutions of the standard quadratic equation. No further explanation is needed when the calculator is used to find the mean and the standard deviation, as long as the text of the question does not explicitly require the candidate to show detailed work. In any other cases, results obtained through the use of a calculator are considered as unexplained and points for such results will not be awarded.
By the way these sheets are publicly available even in English, e.g. from Spring 2019:
Basic level: http://dload.oktatas.educatio.hu/erettsegi/feladatok_2019tav... Advanced level: http://dload.oktatas.educatio.hu/erettsegi/feladatok_2019tav...