The purpose of this study was to investigate the effect of teacher guidance on the quality of collaborative argumentation in middle level classrooms. Each of six science classes was randomly assigned to either the intervention (teacher guidance) or control condition (minimal teacher guidance). The verbal collaborative argumentation that occurred was recorded and transcribed. The researchers conducted an independent-samples t test to analyze the difference of the depth measure of quality between groups and found a significant difference between the means in the depth measure. The findings reveal that using argumentative scripts for teacher guidance led to more in-depth argumentation.