They are open-ended. All activities can be interpreted and completed according to the individual ideas of the teacher and the students. No child should feel reluctant to complete the work out of fear that the final product might be wrong or unacceptable. In fact, students will express themselves most creatively and benefit most fully when you allow them to complete the activities without regard to the almighty grade. They are product focused.
Every activity allows students to concretely demonstrate their thinking and feeling.
Each lesson has a clearly defined beginning, middle, and end as well as a tangible product showing the results of students explorations. Your students conversations may suggest additional possibilities for products. They are teacher and student tested. We are not asking you to teach a lesson that we ourselves have not taught. The samples of student work that accompany many lessons are just a handful of the many original, wise, and multifaceted responses the activities have elicited from children.