I'd have felt really self-conscious bringing a Birkin (or any other expensive fashion accessory) to grad school. It probably depends on your school and program, but in my case, a Birkin was equivalent to a semester's stipend, and that's all a lot of people had to live on. True, your fellow students may not know or care what a Birkin is (especially if they're men), but if one person does, that's the sort of information that will travel fast and possibly cause resentment among other students who have to scrimp just to get by. Again, it really depends, but that's from my experience.