Complex sentence: Nearby, an odd bird-like alien ship appears, and Harlan Band decides to sneak onto it; the other students, all of which are younger and much less troublesome, follow Harlan onto the ship.
Split into simpler sentences: Nearby, an odd bird-like alien ship appears and Harlan Band decides to sneak onto it. The other students, all of which are younger and much less troublesome, follow Harlan onto the ship.