This study explored student abilities in applying conceptual knowledge when presented with structured performance tasks. Specifically, the study gauged proficiency in higher-order applications of students enrolled in earth and environmental science or biology. The student sample was drawn from a Redesigned STEM high school model where a tested performance assessment protocol was employed for the purposes of the investigation. It was determined that performance-based proficiency was not uniform within tasks and applications, but could be recognized through student artifacts of learning on a situational basis. Based on the findings of the study, several implications are highlighted.