Try speed and convenience. Also, when lectures are really boring, you can play games.No reason, unless they have a learning disability and have to have it. It's really distracting hearing people type.
I'm in Germany, where bringing your computers to high school is unheard of, but I still bring my MBP from time to time, but every time there was a reason. Like the other day we were preparing for a biology presentation. Or today, we had a Photoshop unit in art class (easiest good grade ever). If you brought a laptop to class, the teacher would probably think you were trying to provoke them.