earthworms and their curiosity about these animals, and so the question they chose engaged them thoroughly. As they developed answers to their questions, Ms. Flores helped them understand that they needed evidence and what the nature of that evidence needed to be. They looked for evidence through their careful observations and what they read in scientific books. Learning about fair tests increased the likelihood that their evidence would be sound. As they collected their evidence, they built their cases for explanations that addressed their questions. The group looking for favorable environments, observed how the earthworms behaved in “homes” with varying amounts of moisture, and arrived at their explanation of just the right amount; the group examining eating habits observed the numbers of worm holes in different fruits and vegetables and explained worm “preferences” through those data. Throughout the investigations, students developed their own explanations using the evidence they collected and compared them with published scientific explanations from their text books, library books, and the Web. Finally, the students communicated their learning in a variety of ways, clarifying what they did, what results they achieved, and how they knew the results were correct. This communication also served Ms. Flores as an assessment of her students’ understanding of life cycles and their abilities of inquiry. As third graders, Ms. Flores’s students did not begin with well-developed inquiry abilities. But because Ms. Flores realized that using earthworms would involve an investigation extending over several weeks, she took advantage of the fact that she could pay a great deal of attention to developing her students’ inquiry abilities as they learned the subject matter content. Therefore, her students’ inquiry was relatively open, with as much coaching as necessary to make sure that the class had many choices for research questions, had a variety of designs for their investigations, and clearly communicated their results.

Instructional Model. Ms. Flores’s unit illustrates an interesting and complex sequence of learning activities. Early in the unit, she engaged the students repeatedly in direct, firsthand experience, first almost by accident as they stumbled upon the earthworms in their study of the vacant lot. Later Ms. Flores involved them again in examining the area where they originally found the worms so that they could think about what kind of “home” they would build for their worms.

As Ms. Flores focused the students on the questions they generated and the ideas they had about worms, they began to explore the worms’ characteristics, their environments, and their life cycles. They made observations

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