In their daily lives, people use skills of argument in interpersonal interactions with others. Increasingly, they do so online. However, skills of argumentation are not well-taught or learned in schools, nor is their development well-understood in either face-to-face or online environments.

Although Computer-Mediated Communication (CMC) has been found to promote argumentive knowledge construction, it often falls short of its potential, resulting in low levels of learning and unfocused interactions. In some online contexts, argumentation scaffolds have successfully addressed these problems. Most such scaffolds were designed for college students engaged in asynchronous communication. As middle-school students increase their use of instant messaging technologies, it is essential to identify the supports necessary for these learners to communicate their ideas effectively and develop critical skills of argumentation.

The present study was conducted as part of an argumentation curriculum implemented in an urban public middle school. The first year of this curriculum was successful in promoting the development of argumentation skills. It remained to be determined whether these skills could be promoted more effectively with the use of additional scaffolds during online argumentation.

This study explored the efficacy of one particular argumentation scaffold, which required learners to assign functional labels to their messages during online argumentation. Sixty-three 7^th grade students engaged in 10 online argument sessions. Working in same-side pairs, they argued with a series of opposing pairs via instant messaging about two consecutive issues. One group of students (n=32) used the scaffold for some of these sessions; a comparison group (n=31) never used the scaffold.

At posttest, students who used the scaffold performed better on measures of argument recognition. Relative to the comparison group, they more successfully distinguished between strong and weak arguments and showed a preference for stronger argumentive moves. Results were inconclusive as to whether the scaffold also promoted enhanced argument production skills or more effective collaborative processes among learners.

Benefits of this research include implications for instructional design of online learning environments for adolescents. Furthermore, it is of interest to schools genuinely committed to promoting better thinking in their students.