IMO Strauss Alpine Symphony is probably not a great excerpt to represent what a high school senior bassist is capable of. You're going to be judged based on your solo playing primarily, and there are many orchestral excerpts that are often asked for on auditions but feature more musicality and can make you sound comfortable and tension-free. Strauss excerpts in general, while impressive technically under the best circumstances, tend to expose many weaknesses in young players. Mahler 1 or other orchestral solos, Otello...these are opportunities to make music without being pushed to your limits.