One of the most surprising realizations for adults who begin working in schools is that what is taught is not what they were taught or what they think should be taught. Curriculum is a part of school that is affected by many factors; some are very local (individual teachers are ultimately responsible for what it taught in their classrooms), others are school-wide or district-wide, yet others are state-wide or national. In the United States, there is no nationally mandated curriculum, and concepts like “fourth grade mathematics” are variable and open to interpretation.