Authors make the claim that carefully designed integrated STEM assessment/learning tasks can be used appropriately to lead teachers away from teacher-directed and towards more student-directed instructional practice. A conceptual framework of activity theory emphasizing “doing is learning” grounds a twelve-step, principled design approach to design performance assessments also serving as models of reformed iSTEM instructional practices. At each step, lesson/assessment designers apply a recursive, revise-and-reflect process to self-assess the appropriateness of teacher-directed strategies in every lesson within the performance task. Appropriateness refers to the activity level at which an individual student can perform a learning task with the help of others. Based on the novelty and complexity of what students will be actively doing with the information centering the learning activity, the designer chooses a teacher’s role to accommodate students’ abilities to cognitively handle the novelty and complexity of the information. Accordingly, designers decide a need for explanation, clarification, prompting, elaboration, or review before and/or during the lesson. While whole-class, teacher-directed instruction can sometimes be the best and most efficient way for students to begin their work with novel or complex information, reform-based designer/practitioners reserve teacher-directed, non-active learning for only these instances. Otherwise, teachers employ instructional strategies that can meet the needs of individual students by encouraging them to actively work on the information with others. These teachers prefer working with students in small groups to identify and address learning difficulties while maintaining as much student-directed activity as possible.