Si factus illabatur orbis, impavidum ferient ruinae
Meaning if the world were to crash on me, I would be unmoved my the ruins
Notes -
Use if a teacher gives you a bad mark, a great move [not really, but it's up to you] would be to say that phrase. It's simply another way of saying 'I couldn't care less'. If then they lower your grade even more, shame's on you.