I too used to speak up in undergrad classes, though I admit I would even ask questions I knew to be intelligent, but slightly off base so the professor could gently correct me, but I would get credit for participation.
At first, it didn't seem worthwhile to participate in law school. First, at Tulane, at least, no credit is available for participation. (All grades are based on end-of-the-year anonymous exams) Second, you get pegged as a gunner by your fellow classmates.
In the end, I ended up participating just because I'm that sort of guy. I love to be right and to hash out the details. It is why I chose law school and not b school. I had considered transferring immediately upon gaining entrance. Tulane was my safety school and new orleans didn't interest me. New Orleans came to grow on me and it turned out that one of my professors convinced me to apply to transfer! So getting her to write me a recommendation was no problem. I felt out other professors whose class I had gotten an A in.
One indiciated that he felt conflicted and so I didn't ask him. Another was the Dean and so I figured he would be conflicted. The last was happy to do it. All or your professors will likely have gone to a top5 law school and would be happy to see you do well too.