In this essential resource, science educator Page Keeley provides teachers with guidance, suggestions and techniques for using formative assessment to improve teaching and learning in the science classroom. Based on the knowledge that good assessment practices are integral to measuring and documenting student achievement as well as informing teaching and learning, the author addresses the need to balance opportunity to learn, which includes assessment for learning, with assessment of learning. She then identifies and describes a rich and varied repertoire of purposeful strategies that weave assessment throughout instruction and learning. These techniques will help teachers become more aware of the different ideas students bring to their learning, see the connections between students’ thinking and the specific ideas included in standards, and provide learning experiences that build a bridge between their students’ thinking and accepted scientific ideas.