I'm currently preparing an online tool for scholars, and part of that work involves creating a database with different categories for students at different stages of their college/university education (i.e. freshmen, second-semester juniors, first-year graduate students, etc). I'm struggling to find a standard classification system to use that would allow distinction between all of the stages in an undergraduate and graduate education. I could just use "first-semester senior" and the like, but if there's an existing standard - particularly one that even allows for students that don't use semester classifications - I don't want to complicate things with my own classification scheme.
Is there a convention, especially an international convention, that distinguishes between all or most of these stages in educational progress?