What's impressive to a panel of people who will be judging your musical ability is confidence.
It doesn't matter what you play as long as you play it well, and look like you belong where you're standing when you play it. You shouldn't be apologetic for what you're doing, you should be confident and connect with the audience in front of you. If it's a band situation and they provide a rhythm section for you, make sure you talk over the arrangement you're going to play first. Don't be timid, don't hesitate, and be strong. A strong character is what they're looking for at a school. They want students they can improve, and then talk about to advertise their school when you leave. That's a bit of a business standpoint, but it's a reality.
Play Jaco, play bob dylan. It doesn't matter. Just be you, and carry yourself like you deserve to be there. Picture yourself already being a student at the school. Picture yourself walking through the hallways, looking at your class schedule. Make the audition into a situation that you're actually there to accompany someone else's audition. You're already a student there, and you're just helping out and playing music. Natural, and relaxed.
That's what I'd do anyway.
Janek