How can assessments measure complex science learning? Although traditional, multiple-choice items can effectively measure declarative knowledge such as scientific facts or definitions, they are considered less well suited for providing evidence of science inquiry practices such as making observations or designing and conducting investigations. Thus, students who perform very proficiently in "science" as measured by static, conventional tests may have strong factual knowledge but little ability to apply this knowledge to conduct meaningful investigations. As technology has advanced, interactive, simulation-based assessments have the promise of capturing information about these more complex science practice skills. In the current study, we test whether interactive assessments may be more effective than traditional, static assessments at discriminating student proficiency across 3 types of science practices: (a) identifying principles (e.g., recognizing principles), (b) using principles (e.g., applying knowledge to make predictions and generate explanations), and (c) conducting inquiry (e.g., designing experiments). We explore 3 modalities of assessment: "static," most similar to traditional items in which the system presents still images and does not respond to student actions, "active," in which the system presents dynamic portrayals, such as animations, which students can observe and review, and "interactive," in which the system depicts dynamic phenomena and responds to student actions. We use 3 analyses--a generalizability study, confirmatory factor analysis, and multidimensional item response theory--to evaluate how well each assessment modality can distinguish performance on these 3 types of science practices. The comparison of performance on static, active, and interactive items found that interactive assessments might be more effective than static assessments at discriminating student proficiencies for conducting inquiry.