Does the scientific practice of modeling actually support students in making thinking visible? Middle school teachers can build from the work of 12 K–8 teachers who wanted to learn how the practice of modeling is developed across grades and analyze how those skills end up looking in middle school. They gave their students the same phenomenon and prompts, tried them out with their students, collected models to compare them, and then came together across two years to discuss modeling. All students across the grades showed similarities in the models, both in terms of how they presented ideas and the scientific ideas. Many middle school models looked similar to those in early grades, and although middle school students showed particles of air in the models, the usefulness of the particles to explain the phenomenon was almost always unclear from the models alone. Implications for assessment of middle school students include discussing models with students to assess their knowledge and including fewer student scaffolds at the onset.