Schools use a variety of ways to group students for instruction; most prevalent in middle level schools seems to be ability grouping. Arguments once considered persuasive for ability grouping are losing influence given evidence that the practice results in few achievement benefits and several negative effects. This Digest discusses attitudes toward tracking, summarizes research on ability grouping and tracking, and provides suggestions for further research. Proponents of tracking argue that tracking helps schools meet the varying needs of students, provides low-achieving students with increased attention and a slower work pace, and allows high-achieving students to be challenged by faster-paced, more-demanding lessons. Those opposed to tracking are concerned about the perceived psychological damage to low achievers, the slower pace and lower quality of instruction, the more inexperienced or sometimes less-capable teachers assigned to teach lower-ability students, the low expectations for student performance held by teachers, and the absence of strong peer role models in classes for low-ability students. A survey of principals indicated that ability grouping is present in many middle schools, although some schools are considering implementing other strategies. Research indicated that teachers who wish to retain ability grouping are more subject centered, and those who wish to eliminate it are more student centered. Other research indicated that ability grouping makes the school schedule less flexible, and that after the elimination of tracking, teachers reported positive social benefits, positive behavioral implications, positive academic benefits, and less parental competition. Studies of mathematics tracking found no positive long-term effects for low-ability students who were placed in low-grouped classes, positive effects for average-achieving students placed in high-track classes, and no negative effects for high-achieving students in computation or problem-solving achievement and positive effects in concept development. Researchers suggest the need for further research to determine long-term effects of tracking and effective alternatives. (LPP)