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Problem-based learning (PBL) and project-based science (PBS) are increasingly popular approaches for engaging students in scientific inquiry. Though these approaches have different origins, they are similar in practice. Both PBL and PBS are centered on authentic problems or meaningful questions that serve to organize learning. Both are student-oriented and experiential–students solve a problem by practically applying science concepts (Hmelo-Silver 2004). [FIGURE 1 OMITTED] During PBL and PBS, students conduct research on a science topic and gather relevant information to devise a solution or create a product (Barrows 1996; Marx et al. 1997). They develop knowledge and understanding of scientific ideas by planning investigations, gathering evidence, using previous research, proposing possible explanations or hypotheses, and communicating their findings–hallmarks of authentic science inquiry (NRC 2000). Due to the student-centered nature of PBL and PBS, it is easy for teachers not to provide students with adequate feedback or enough support to promote critical thinking. However, research has shown that PBL and PBS are most effective when appropriate learning goals are defined, embedded supports and feedback are part of instruction, and there are multiple opportunities for self-assessment and revision (Barron et al. 1998).
Instructional supports for student learning come in many forms. In this article, we describe how formative assessment can be used to support PBL and PBS to maximize student achievement. Formative assessment: A primer Formative assessment is assessment for learning, not assessment of learning, which is common in end-of-unit tests (Black and Wiliam 1998). Formative assessment is any pedagogical strategy used to elicit student understanding at any point during instruction. For formative assessment to be most successful, teachers must use the outcomes to make instructional decisions and provide feedback that directs learning. In fact, formative assessment should be a cyclical activity that occurs several times in a PBL or PBS unit (Figure 1).
FIGURE 2 Example T-chart. This chart is used to elicit students’ prior knowledge and interests in science topics. Topic: Stars and their life cycle What I know about stars Questions I have about stars and their life cycle Embedding formative assessment Beginning with the end in mind Planning a PBL or PBS unit can be daunting. However, through formative assessment, a teacher can more readily identify students’ interests, which can be used as the starting point for planning instruction. Teachers can begin by identifying a general focus area (e.g., the rock cycle, genetic engineering, space exploration) that aligns with state content standards and use it to probe students’ prior knowledge and personal interests. Several common pedagogical strategies can be used to formatively assess students’ knowledge and interests. For instance, a KWL chart–What I .Know, What I Want to Know, What I Learned–is often modified for the project-based classroom. In this version, students answer a set of need-to-know questions at the beginning of a project (Chin and Chia 2008), such as * What do I know about this problem? * What do I need to know to provide a solution? and * How can I find out what I need to know? These questions provide students with necessary direction and provide the teacher with valuable insights about their prior knowledge, their alternative conceptions about science content, and potential problem areas during learning. FIGURE 3 Background knowledge probe example. It is estimated that 99% of the species that have lived on Earth are extinct (Cowen 2000). However, only a small number of these organisms have been found as fossils. Why are there so few fossils from all the plants and animals that have lived on Earth?
