Due to government initiatives, education in the classroom has focused on high stakes test scores measuring student achievement on basic skills. The purpose of this action research study was to augment fourth grade students' knowledge of basic content by teaching greater meaning and depth of understanding--to teach critical thinking using Socratic circles. Using a constructivist approach, a comprehensive plan was designed and implemented that included an age-appropriate platform for argument and inquiry, a process that required critical thinking skills, and allowed the intellectual standards for critical thinking to be developed and measured. Ten students representing the academic levels of the whole class were selected and participated in seven Socratic circles. Over a period of 15 weeks, a mixed methods approach was employed to determine how students were able to apply the intellectual standards to reasoning during Socratic circles, how this innovation provoked participation in student-centered dialogue, and how Socratic circles improved students' evaluation of competing ideas during their reasoned discourse. Results suggested that Comprehensive Socratic Circles increased participation in reasoned discourse. Students' ability to evaluate competing ideas improved, and their application of the intellectual standards for critical thinking to their reasoning increased. Students also increased their use of student-centered dialogue across the sessions. These findings suggest that Socratic circles is a flexible and effective teaching strategy that fosters critical thinking in fourth graders.