How can we assess the core scientific knowledge and skills that students need to succeed in the 21st century? Dynamic assessments expand how phenomena, information, and data can be represented and increase the number of ways learners can show their knowledge and skills. The challenges for K-12 educators and assessment developers are to create assessment tasks that allow students to demonstrate 21st century scientific skills and evidence models for making inferences about student proficiency. In this symposium, researchers who are developing simulation-based assessments to meaningfully assess science content and inquiry skills will use the conceptual framework of evidence-centered design to structure presentations of their science assessment projects. Presentations will be followed by discussions from experts in assessment design.