For teacher librarians who do coteaching, this is a very important book. The author envisions a group of teachers, let’s say a group of third grade teachers, sitting down to plan a unit of instructing and jointly planning the assessments that will be used by everyone in the group. The author emphasizes formative assessments so that changes can be made in the teaching plan as the unit progresses. Erkens also proposes that any data from state or national tests be stirred into the pot as further evidence. She has a model plan for the developing the various assessments that at first glance seems to be rather complicated and time consuming, but after a bit of explanation with the examples, a group of experienced teachers could use this system without a great deal of difficulty. What Erkens does not anticipate is a teacher librarian who is joining the planning team and who wants to embed reading, inquiry, information, and technology carefully into the mix to boost the teacher’sagenda. In this case, the assessments need to be stretched a bit to ascertain whether the combined agendas work. Not difficult, but we wish our fellow education experts would recognize what we have to offer and include us. If you have not already had a lot of professional development on assessment and need to propose some, this book is an important one to consider Highly recommended.