Past research has identified elements underlying modeling as a core science and engineering practice, as well as dimensions along which students' learn how to use models and how they perceive the nature of modeling. To extend these findings by a perspective on how modeling practice can be used in classrooms, we used design-based research to investigate how the modeling practice elements, i.e., construct, use, evaluate, and revise, were integrated in a middle school unit about water quality that included using an online modeling tool. We focus on N = 3 groups as cases to track and analyze 7th grade students' modeling practice and metamodeling knowledge across the unit. Students constructed, used, evaluated, and revised their models based on data they collected and concepts they learned. Results indicate most students succeeded in constructing complex models using the modeling tool by consecutively adding and specifying variables and relationships. This is a positive finding compared to prior research on students' metamodeling knowledge. Similar to these studies, we observed several basic metamodeling conceptions and generally less progress in this field than in students' models. We discuss implications for applying modeling practice in classrooms and explain how students make use of the different modeling practice elements by developing their models in the complexity and quality dimensions.