Why do different publishers give two similar pieces of music different difficulty levels?

Each publisher maintains its own set of guidelines to determine difficulty levels, sometimes influenced by the state's standards where they are located. On this website, you'll see Pepper lists difficulty grades using one set of guidelines for all music, regardless of publisher, striving for maximum consistency for you. Just as two different publishers may grade a similar piece differently, you will sometimes see that the Pepper level differs from the publisher's.