This research reports on a study of curriculum materials development and use compared with the use of existing curriculum materials in an elementary classroom. The research explored the effect of explicit attention to epistemic practices in curriculum materials and the enactment of those materials. Epistemic practices include asking questions, collecting data, making descriptions of observations, finding patterns in the data, and developing scientific reasoning. Scaffolding considered the function, role, and purpose of epistemic practices in the community of science and the production of scientific knowledge. The designed curriculum was compared with an existing pedagogically similar curriculum to consider whether the scaffolding and explicitness affected enactment. Findings lead to the conclusion that enactment was impacted. Specifically, findings show that scaffolding in materials created more instances of students engaging in scientific reasoning. Similarly, the explicit description of epistemic practices supported the teacher in explicitly providing opportunities for children to learn about and use epistemic practices of science. Finally, when using the designed curriculum, teacher modifications during enactment showed to be more consistent with the intended instructional approach and also helpful for children in learning epistemic practices of science. © 2007 Wiley Periodicals, Inc. Sci Ed92:608–630, 2008