The glockenspiel (otherwise known as bells) are considered a percussion instrument because you use a mallet to strike the key to produce a sound. The bells’ keys are laid out identical to a piano, and the notes are the same as the notes on a piano. A student who has piano experience and wants to play something similar in a school music setting should consider the bells.
The bells often play the notes along with the flutes, but sometimes have separate parts written out. Typically, the bells are part of a “percussion kit” which include the bells, stand, practice pad, drum sticks, and bell mallets.