This paper argues that for most of the 20th century, schools have constructed multiple categories of “unlikeness” or unlike ability, and that these categories were created or soon appropriated to mean “children who cannot learn together.” Important evidence collected throughout the century, but most especially in the past twenty years, reveals that school categories favoring children’s likeness, rather than their “unlikeness” promise to improve educational fairness and the country’s educational quality. Ability grouping has been bolstered by the argument that equal opportunity in a democracy requires schools to provide each student access to the kind of knowledge and skills that best suit his or her abilities and likely adult lives. To make the argument more palatable in a culture that, rhetorically at least, values classless and colorblind policies, educators and policymakers have reified categorical differences among people. So, in contemporary schools, there are “gifted” students, “average” students, “Title I” students, “learning disabled” students, and so on, in order to justify the different access and opportunities students receive. Assessment and evaluation technology permits schools to categorize, compare, rank, and assign value to students’ abilities and achievements in relationship to one another (as well as to students in other schools, states, and countries-past and present). Homogeneous grouping began in earnest early in the 20th century. It matched the prevailing IQ conception of intelligence, behavioral theories of learning, a transmission and training model of teaching, and the factory model of school organization. It fit with schools’ role in maintaining a social and economic order in which those with power and privilege routinely pass on their advantages to their children. Homogeneous grouping embodied a belief that permeated schooling during the 20th century-that we understand most about students when we look at their differences, and the more differences that can be identified, the better our understanding and teaching. Homogeneous grouping provided policymakers and educators a way to “solve” an array of problems attributed to the growing diversity of students. New immigrants needed to learn English and American ways. Factories needed trained workers. Urban youth needed supervision. And schools needed to continue their traditional role of providing high-status knowledge to prepare some students for the professions. Policymakers defined equal educational opportunity as giving all students the chance to prepare for largely predetermined and certainly different adult lives. Concurrently, two phenomena shaped a uniquely American definition of democratic schooling: (1) universal schooling would give all students some access to knowledge; (2) IQ could justify differentiated access to knowledge as a hallmark of democratic fairness. While most current grouping practices don’t rely on IQ-at least exclusively-the early dependence upon it set a pattern that continues today. Standardized achievement tests, strikingly similar to IQ tests, play an important role in dividing students into ability groups and qualifying students for compensatory education programs; standardized language proficiency tests determine which class “level” is appropriate for limited English students. In conjunction with other measures, IQ remains central in the identification of gifted and cognitively disabled students.Over the course of the 20th century, compulsory education laws and the necessity of a highschool diploma drew more and more students to school-even those previously considered uneducable. States and local school systems developed an array of special programs for students who, in earlier times, simply would not have been in school. By the 1960s, the federal government had turned to special categorical programs as its principal way to guarantee education for all American students. The Elementary and Secondary Education Act (ESEA) provided categorical funding for “educationally deprived” students. Lau et. al. v. Nichols et. al. was brought on behalf of Chinese students in San Francisco and led to legislation requiring that all schools provide special assistance to their students whose native language is not English. The Individuals with Disabilities Education Act (IDEA) provided funds to classify students with physical and neurological problems and provide these students with special education programs when it was believed that they could not be accommodated in regular programs. Advocates for “gifted” students increasingly used the “bell curve” logic to argue that the gifted and the cognitively disabled are like a pair of bookends, and that those at the high end of the curve also required special support because they are as different from “normal” students as the disabled. Educators responded in culturally predictable ways. They identified students who were “different,” diagnosed their differences as scientifically as possible, and assigned them to a category. They then grouped students for instruction with others in the same category and tailored curriculum and teaching to what each group “needs” and what the culture expects. So, today, educators routinely assign “normal” students to “regular” classes at different levels (e.g., high, average, slow). They place the others in “special” programs for learning disabled, behavioral problems, gifted, limited English, poverty-related academic deficiencies, and more. Within homogenous groups, teachers assume students can move lock step through lessons and that all class members will profit from the same instruction on the same content at the same pace. Lurking just beneath the surface of these highly rationalized practices, however, are the illusion of homogeneity, the social construction of classifications, the prevailing biases of race and social class, and self-fulfilling prophesies of opportunities and outcomes.The considerable student differences within supposedly homogenous classes are obvious and well documented. And yet, for most people, the characteristics and categories by which students are sorted remain more salient than the “exceptions” that impugn those categories. Many educational constructs, including those used to classify students, began as narrowly defined, highly specialized, technical terms or measures. However, as they make their way from research to professional journals and teacher preparation programs to popular media to the everyday talk of policymakers and the public, they loose their narrow definitions and specialized uses. What may have begun as specific technical concepts or as informal notions such as “at risk,” “gifted,” “high ability,” “college prep,” “attention deficit,” “hyperactive,” “handicapped,” etc. are quickly reified and become a deeply embedded feature of students’ identities in their own and others’ minds. African American, Latino, and low-income students are consistently overrepresented in low-ability, remedial, and special education classes and programs. This is not surprising, given that grouping practices grew from the once accepted practice of preparing students of different racial, ethnic and social-class backgrounds for their separate (and unequal) places in society. In part, placement patterns reflect differences in minority and white students’ learning opportunities that affect their preparation and achievements. But they also reflect the fact that US schools use white, largely middle-class standards of culture and language styles to screen for academic ability and talent. Teachers and school psychologists sometimes mistake the language and dialect differences of Hispanic and Black students for poor language skills, conceptual misunderstandings, or even poor attitudes. An additional hazard for students of color is that schools often confuse cultural differences with cognitive disabilities, particularly retardation. Researchers have noted for the past 25 years that students with identical IQs but different race and social class have been classified and treated very differently in special education placements. The misidentification problem triggered both federal and state court decisions requiring that potentially disabled students receive due process. In a far reaching decision, the California courts ruled in Larry P. v. Wilson Riles (1979) that schools could no longer use intelligence tests to identify minority students as mentally retarded. However, substantial problems remain and new ones emerge, including recent evidence that African American boys are disproportionately identified as having Attention Deficit Hyperactivity Disorder (ADHD).Placement in a low class becomes a self-fulfilling prophecy of low expectations, fewer opportunities, and poor academic performance. Poor performance begins the cycle anew, giving additional justification to schools to reduce expectations and opportunities. Extensive research makes clear that, in every aspect of what makes for a quality education, kids in lower tracks typically get less than those in higher tracks and gifted programs. Finally, grouping practices help shape students’ identities, status, and expectations for themselves. Both students and adults mistake labels such as “gifted,” “honor student,” “average,” “remedial,” “learning disabled,” and “mild mental retardation” for certification of overall ability or worth. Everyone without the “gifted” label has the de facto label of “not gifted.” The resource classroom is a low-status place and students who go there are low status students. The result of all this is that most students have needlessly low self-concepts and schools have low expectations. These recommendations reflect growing support for heterogeneous grouping as necessary to ensure that all students have access to high-quality curriculum, teachers, and learning experiences. For example, early analyses of the disappointing performance of U.S. students on the Trends in International Mathematics and Science Study (TIMSS) support mounting concerns that the low scores stem, in part, from the tracking of most American students in less academically demanding math and science classes. Increasingly, educators and policymakers are developing an awareness that schools cannot teach or achieve social justice unless they eliminate grouping practices. A number of school desegregation cases have cited the practice as a source of continuing racial discrimination. However, this goal will not be accomplished quickly, and policy reports will simply gather dust unless enlightened educators understand and act to change the norms and political relations these grouping practices embody. There is a long, hard road ahead.