The authority to set standards of learning, by virtue of the US Constitution, is delegated to the states. Recognizing differences in standards from state to state and the need for the reform of mathematics education programs, the NCTM initiated a process of developing national standards for mathematics curriculum. The Standards asserted that every student needed to explore topics from number, algebra, geometry, discrete mathematics, statistics, and probability, regardless of academic ability, gender, race, culture, or socioeconomic background. In some cases, objectives emphasize paper-and-pencil symbol manipulation, memorization of terms and definitions, or writing explanations or proofs. In crossover model, all students explore the same core of objectives but at a different level of depth in the differentiated model. The idea of integrating the curriculum is no stranger to the middle school classroom. Educators usually group objectives into three categories—affective, cognitive, and psychomotor.