This study examines whether middle-school students’ dense, extended engagement in an argumentation curriculum promoted development of argument skills, specifically increased use of direct counterargument and improved argument evaluation skill. A total of 56 students in two classes participated twice a week for three years (grades 6, 7, and 8) as part of their regular school curriculum. Students attended an urban middle school affiliated with a large university and were predominantly Hispanic and African-American and from lower and lower-middle socioeconomic backgrounds; 20% were from middle-class Caucasian families. In addition to its central element–electronically conducted pair dialogs on social issues-the curriculum encompassed a range of activities including small group preparation of arguments and reflective activities. A third class of 23 served as a comparison group; they also met twice a week over the same time period. They addressed similar social issues in more traditional whole-class discussion and wrote essays.