Bud learns more than one life lesson over the course of this relatively short novel. A common answer is that Bud learns the value of family, and that is definitely true; however, I don't believe that life lesson is earth-shattering to Bud. I think Bud has always known the importance of family. His mother had a huge impact on Bud's life, and her death cemented the idea that losing her (his family) is a big deal. Finding his real family is what drives Bud throughout the book. He wants his father because he believes that his life can be made more whole with the presence of a blood relative. Bud does eventually find a blood relative, but Bud also learns that family doesn't have to be blood kin. Bud learns that the basis of a family is love. Calloway's band embraces Bud as one of their own, and Bud is once again reminded of what it feels like to have a loving family. He's been missing it since his mother died.

I think another important life lesson that Bud learns over the course of this story is perseverance. Bud simply refuses to give up his search for his family. He is met with considerable hardships and events that steer him slightly off course; however, Bud learns what his mother meant about doors being opened. She told him that when one door closes, another door is opened. Bud was too young to understand that she wasn't speaking of literal doors. Bud comes to understand that it's okay to have a door closed as long as he's willing to keep pushing through the new door that has been opened for him.

Bud, Not Buddy is a bildungsroman (or a coming-of-age story); therefore, it contains many life lessons for Bud. For example, Bud learns how to survive during the Great Depression. However, that is not Bud's most important lesson. In particular, Bud learns the true meaning of family.

The first way Bud learns about family is by experiencing ways that he does not fit within other particular families. First, the reader sees Bud being abused by the Amos family (Bud's foster family). Mrs. Amos does not even “hear” Bud over her own son (who can do no wrong). Further, being locked in a shed with a threat of a beating is certainly child abuse. The Amos family, then, is not Bud’s true family. Later, we meet the family that helps Bud at the mission. 

I watched them walking away. My pretend brother looked back at me and stuck out his tongue, then reached up and took my pretend mother's hand. I couldn't really blame him.

Even though the family helps Bud, they do not adopt Bud as their own. The children in the family are disgusted by having to share their sweets with Bud. These two families (as well as others) can be compared with Bud’s real family: the jazz band.

The most important way Bud learns about family is by finding his own family with the context of Calloway's band. The jazz band, even though it is not a “typical” family, is a perfect and “real” family for Bud. Bud is accepted and welcomed into this family. Further, he is given his livelihood by this family (his “skinny wooden flute” and his saxophone). Bud is also required to provide for the family in what ways he can. Specifically, Bud is asked to help clean and learn multiple instruments. In these ways, Bud finds the home he has been looking for within the jazz band.