A curriculum unit for middle school Earth Science called "What's on Your Plate?" was designed. The unit was implemented in several middle and high school classrooms in California and Massachusetts. In the first implementation, the total number of students who participated was 1100. The unit was designed with two main pedagogical principles: make thinking visible, and help students learn from one another; both were derived from an inquiry-based framework. With these two main pedagogical principles as a larger guiding framework, we designed the curriculum to provide students with rich, iterative model-based activities for students to both learn with and provide criteria for them to critique their peers' work from the opposite coast. The goal here was to influence students' understanding of the domain as well as their understanding of the nature of models in science by engaging them in an authentic context in which they constructed and reasoned with models, as well as critiqued the models of their peers. Data from 15 classrooms is described both in terms of the gains students made of their understanding of the nature of models as measured by pencil and paper survey administered both before and after the unit. In addition, a small subset of students' data is shown to illustrate advances in students' understanding of models. Lastly, we show how students with more sophisticated epistemologies of models are better able to further their content understanding as compared to students with less sophisticated epistemologies of models.