In their recent book, Classroom Instruction that Works, Robert Marzano, Debra Pickering, and Jane Pollock (2001) advocate cooperative learning as one of the most proven approaches to increasing achievement. They note that cooperative learning has an effect size of .78 compared to methods in which students work as individuals. This effect size places cooperative learning among the strongest of all methods for increasing academic achievement.

The empirical work summarized by Marzano and his coauthors, however, indicates that merely placing students in groups and having them interact will not necessarily produce gains. They offer a warning: cooperative learning "is misused when the tasks are not well structured."

When cooperative learning is structured well to include the basic principles, the positive outcomes are many and dramatic. The Kagan structures are designed to do exactly what Marzano and his coauthors call for – to adhere to the principles of cooperative learning through the use of well-structured tasks.

Basic principles of cooperative learning are summarized in the acronym PIES:

Positive Interdependence:
Positive interdependence occurs when there is a positive correlation among outcomes; negative interdependence is a negative correlation among outcomes. That is, we are positively interdependent when a gain for one is a gain for another and we therefore feel ourselves to be on the same side. We are negatively interdependent when a gain for one can be obtained only by a loss for another, in which case we feel ourselves to be in competition. In the Whole Class Question-Answer structure there are important elements of negative interdependence: When a teacher asks a question, many students raise their hands. As one student is called upon, the others who a moment before were excitedly waving their hands signal their disappointment as they lower their hands -- the gain for one (being called on) is a loss for another. If the selected student hesitates or begins to miss the question, the other students wave their hands with glee, the loss of their classmate is a gain for them. Only if the answering student fails can the other students win an opportunity to be called upon. Inadvertently the students have been set against each other. A gain for one is a loss for another. The students do not experience themselves on the same side. This negative interdependence undermines desired social outcomes such as sharing, caring, helping, and empathy.

Individual Accountability:
In the Whole Class Question-Answer structure teachers call on volunteers, asking "Can anyone tell me...?" "Who would like to...?" or "I need a volunteer to share..." Any student can avoid being called upon by simply not raising his/her hand, violating the principle of Individual Accountability. Because students know there is no required individual accountability, many do not put in their best effort. For example, students are aware that no one will know if they are daydreaming in class: They do not have to be engaged.

Equal Participation:
During Whole Class Question-Answer as we move beyond kindergarten and first grade where all students raise their hands, only a subset of the class always or almost always raises their hands. As we move up the grades, a larger and larger subset seldom or never do, violating the principle of Equal Participation.

Simultaneous Interaction:
During Whole Class Question-Answer only one student at a time is called on, leading to very little overall overt active participation, violating the principle of Simultaneous Interaction. In six minutes of Whole Class Question-Answer, the teacher can call upon and respond to about three students. Subtracting time for the teacher to ask each question, call on each student, and respond to each answer, in the six minutes, the three students receive at most about a minute each to verbalize their answers. Most of the class is not actively involved. One-at-a-time participation amounts to little overall engagement for most students because it takes thirty minutes to listen to each student in the class for one minute if they speak one at a time. During that thirty minutes, each student has been an active participant for only one minute.