It sounds like you need a mentor. Unfortunately neither Code Review nor Stack Overflow provide mentoring, they only provide reviews (CR) or answers (SO). I suggest you to split your new feature ("read all names, ids and grades, and sort them according to x,y,z") into several, e.g. "Write a program that reads student IDs, names and grades, and then prints them in the same order they were given". When you manage that task, you can post your result on Code Review to get some feedback. Alternatively, you can try to sort an array. Or: before you build a Lego Minas Tirith, build a small house :). —
Zeta 39 secs ago