Multi-instrumentalist help music ed admission?

Thanks for all of these very thoughtful responses! Momofbassist, his primary string instrument is viola - 8 years. But his primary interest right now is definitely percussion (he marched a world class drum corps this past summer and is going back next summer). It’s an interesting mix because he has the theory from viola but the rhythm training from percussion (his orchestra teacher loves him because he can count out the complex time signatures!).