This study measures the effectiveness of Collaborative Learning Assessment through Dialogue (CLAD) on reading achievement in inclusive classrooms in the USA. The CLAD process involved students collaboratively completing multiple-choice quizzes, using dialogue and critical thinking to reach consensus and receiving immediate feedback on their responses. The procedure was implemented in three third-grade classrooms (n = 30) in a midwestern elementary school for the purpose of reducing a significant achievement gap between these students and those who attended a different school within the same district (n = 95). The effectiveness of CLAD was assessed though a comparison of students' scores on a state reading achievement test designed to measure their ability to construct, examine, and extend meaning in text. The test was administered to both groups in October 2003 and again in March 2004. While both the intervention and comparison groups showed significant improvement in reading achievement scores, the intervention group showed significantly greater growth with a mean growth rate of 19.78 (0.004) and effect size of 0.60. The achievement gap between the two groups of students was reduced from a 13-point gap in their mean scores to a three-point gap. (Contains 3 tables.)