Well, I suggest you right now train your guys abit, like Squall to lvl 15, and whatever Quistis's lvl is when Squall is 15, its fine. Then, after the SeeD exam, I suggest you start training Zell and Selphie too... not to mention Squall to lvl 20-25. When you are lvl 30 or over in the SeeD field exam, you get a rank of an 'A'. But you can always get an 'A' without getting to lvl 30, but it makes the game easier if you lvl.