Dear
Your question is considerable.
Student in farsi =دانش آموز it is used for students before going to the university. After that we say: دانشجو
And it is not merely for adult people
Adult people in institutes, language schools are called : دانشجو even though they didn't, t go to the university because we can say to someone who is thirty دانش آموز it is really impolite way of addressing.