This study explored teachers' use of the Argumentation and Evaluation Intervention (AEI) and associated graphic organizer to enhance the performance of students in middle and secondary science classrooms. The results reported here are from the third year of a design study during which the procedures were developed in collaboration with teachers. A quasi-experimental pretest-posttest design with 8 experimental and 8 control teachers was used with a total of 282 students. An open-ended test assessed students' abilities to evaluate a scientific argument made in an article. The students were asked to identify the claim and its qualifiers, identify and evaluate the evidence given for the claim, examine the reasoning in support of the claim, consider counterarguments, and construct and explain a conclusion about the claim. The quality of students' responses was assessed using a scoring rubric for each step of the argumentation process. Findings indicated a significantly higher overall score and large effect size in favor of students who were instructed using the AEI compared to students who received traditional lecture-discussion instruction. Subgroup and subscale scores are also presented. Teacher satisfaction and student satisfaction and confidence levels are reported.