Don't drop out if you're not in the top 20% of your class. You'd be an idiot if you did. My first exam last year (my 1L year) is the worst grade I've gotten so far... a B-. It was the first grade I got back. I did well enough on the rest of my exams that semester and was sitting at around the top 20-25% mark. Then second semester, I did really well and jumped to the top 12%. So just because you have a bad exam or two first semester doesn't mean you can't make it up. Good grades are important if you want to work in Biglaw, but don't drop out just because of a bad grade or two.