After many years of believing that I was using discussion effectively in my science classroom, I came across the book: Education for Judgment: The Artistry of Discussion Leadership, edited by C. Roland Christensen, David A. Garvin, and Ann Sweet. It is an invaluable resource for reviewing what one thinks they know about discussion, as well as learning more about what it takes to build a discussion based classroom. In this book I found ways to fix what I knew wasn't working as well as reinforcement for what I was doing right.

The following ideas are taken from the book as I found them the most enlightening in my own efforts to continue to bring real discussion into my science classroom.

From Chapter 8 - With Open Ears: Listening and the Art of Discussion Leading by Herman B. Leonard

"A true discussion is not a question-and-answer session but a connected series of spoken ideas. Listening is the glue that holds together the whole process of questions, answers, and comments."

Herman B. Leonard

• "Get off on the right foot" - Building a discussion based classroom depends on establishing expectations on day one. That is when students sort out the stated rules--those that are expressed verbally and in writing--of the classroom from the "implied" rules--those that are represented in day to day experience.
• "Discuss listening explicitly" - In a true discussion classroom most of the time is spent in active listening while others speak. We are (both teachers and students) out of practice because we are more tuned into lecture based classrooms, a dialogue about what listening is can begin to establish important ground rules.
• "Develop exercises to build listening" - Use specific listening techniques, such as the dyad, to model how difficult listening is. The dyad technique is a great way to start off a discussion as it can begin to uncover important issues that will be valuable later on as the discussion progresses.
• "Reinforce continuity in discussion" - Reinforce comments that move the discussion forward and are built on previous comments. Acknowledge comments that are not on track, but be firm about the need to stay on track, and redirect the discussion if necessary.
• "Pose open but approachable questions" - Try to find questions that are open to careful analysis. Especially in the science class, we need to address questions that are testable, provide avenues of research (either through the literature, or experiment) and stand up to scientific scrutiny.
• "Create a physical space that supports discussion" - Avoid the instructor in front syndrome, you want to get away from any one person being the final authority that the class turns to. If possible, break the class into smaller groups where everyone can face each other.

"There is a body of knowledge that must be conveyed...it is usually not enough that students leave a science course with a general idea of the laws of motion; they must also know something about how to apply them precisely in particular situations."
Bruce Greenwald

• "Try to limit students to relatively short contributions, each of which makes a single major point." Too much, too soon overwhelms and distracts from the discussion. Also, by encouraging short contributions you will allow more students to participate. This is important, especially when first establishing a discussion based classroom, since it keeps the "experts" from taking over the discussion.
• "If a student makes a comment that contains multiple points leading in different directions, rephrase the contribution to emphasize one of those points before asking the class for responses." Try to focus on the one key point that moves the discussion forward. Be sure, however, to acknowledge the contribution, and take note of points you might want to follow up with the student outside of class. This will keep you from discouraging a diverse thinker while at the same time keeping the discussion moving.
• "Short internal summaries are a useful device for focusing a discussion and redirecting it toward a selected issue." By keeping your comments short and to the point, or better yet, encouraging students to summarize the discussion, you will resist "taking over" the discussion and turning it into a lecture.
• "Tangential points should be treated carefully and, for the most part, suppressed." Most classes have their experts who try to refocus any discussion back into their own area of knowledge. To keep these students from distractive or discussion killing side roads, redirect the discussion quickly. You may want to avoid calling on the expert in situations where you know they will have an opening to disrupt the discussion.
• "Close questioning of a single student is an effective way to elucidate a method of approach or calculation." When time is limited you might need to take advantage of students who seem to be leading the discussion down a fruitful path. Especially when you are dealing with discussion based on readings or problems the students were to have done previous to class. Concentrating the discussion on those students who are prepared can reinforce the need for all students to be prepared as well as keeping the discussion going. This is also beneficial when a student is close to an individual breakthrough that will serve as an example to the entire class.
• "Questions from students should almost always be referred first to other students." This should be obvious, but I find it hard, even after years of teaching, to keep from seizing control and answering questions. The confidence that is to be gained, both by the student that answers the question, and by the class as a whole as they realize that you trust them to come up with answers, will support building an environment conducive to open discussion.
• "Try to pose tightly focused, unambiguous questions in directing the discussion." In trying to keep yourself from becoming the focal point of the discussion, resist asking too many questions. When you do ask questions, make sure they are questions designed to quickly redirect rather than start an entire new line of discussion.
• "The weight of critical response and pressure should be directly related to a student's confidence and command of the material." Students that can handle and grow from a more intense challenge should be questioned closely, while those that shrink from intellectual confrontation should be brought along outside the spotlight of class discussion.

Christensen, C.R., Garvin, D.A., and Sweet, Ann, editors, Education for Judgment: The Artistry of Discussion Leadership (Boston: Harvard Business School Press, 1991)