Also, does anyone have any advice on how to ask for a recommendation without offending the school/professor?
I've given that a lot of thought. Face it, in T-4 land, your profs didn't go to your school. They understand the desire to go to a good school. This is where establishing some rapport with the professor throughout the semester will probably yield some good results. It's a lot to expect that if all they know about you is that you handed in an anonymous exam that ended up getting a good grade, that they would then feel comfortable recommending you for something.
If you participate in their class (in a positive manner), and they know your name, that's a good start. If you've stopped by during office hours to talk to them about an area of the law where they have a particular expertise, all the better.
If you've done those two things, you'll have established yourself as a student whom they probably appreciate. As such, chances are they'll want to see you do well.
Although law profs know what side their bread is buttered on, they also view themselves as fiercely independent. So, for a student they don't know from Adam, they might well think, "Hey, why not stay here and keep paying my salary." But for a student they have made a personal connection with, I'd say they're more likely to think of you as somebody they want to help. Regardless of how it impacts their employer, they're likely to want to help you. Good professors, at least, are in this to try and help people, or at least that's somewhere in their mix of motivations.