Ensuring+accountability

How do I ensure accountability when students are working in groups?
Helping students complete projects in groups is like playing a pinball machine. If you just start the ball into play and do not review the machine, you probably will have a short run. In this same thinking, if you just let students begin working and problems will begin almost immediately. On the other hand, if you review the machine's options before you start the ball you will have a much more enjoyable pinball experience. In this same view, preparation on a teacher's part will help ensure students remain engaged and participate in the project.

Concerns:
 * Some students will sit and not participate with group.
 * Some students will dominate conversations and work completed.

Solutions
 * An engaging "Essential Question" with student friendly "Unit and Content Questions" has worked in my classroom to keep students focused and participating.
 * Provide a detailed description of individual assignments for tasks.
 * Provide each student a checklist to self complete indicating their work on specific task assignments.