When learning orchestral excerpts, it's absolutely imperative to learn more about what you are playing. You must understand the context for your excerpt within the larger work and how your excerpt fits together with other instruments playing at the same time.
For each of the grades listed below, you can find links to the score for each work and videos showing the excerpt in question, a segment of the composition, or the work as a whole. Of course, these videos are only some of the many available online. Use this as a starting point and continue to listen to as many recordings and videos as possible. Conductors and performers interpret music in vastly different ways and it's important to create your own musical style while being mindful of performance practice and current musical trends.