ICAP is a theory of active learning that differentiates students' engagement based on their behaviors. ICAP postulates that Interactive engagement, demonstrated by co-generative collaborative behaviors, is superior for learning to "Constructive" engagement, indicated by generative behaviors. Both kinds of engagement exceed the benefits of "Active" or "Passive" engagement, marked by manipulative and attentive behaviors, respectively. This paper discusses a 5-year project that attempted to translate ICAP into a theory of instruction using five successive measures: (a) teachers' understanding of ICAP after completing an online module, (b) their success at designing lesson plans using different ICAP modes, (c) fidelity of teachers' classroom implementation, (d) modes of students' enacted behaviors, and (e) students' learning outcomes. Although teachers had minimal success in designing "Constructive" and "Interactive" activities, students nevertheless learned significantly more in the context of "Constructive" than "Active" activities. We discuss reasons for teachers' overall difficulty in designing and eliciting "Interactive" engagement.