Cognitive neuroscience research is typically conducted in controlled laboratory environments and therefore its contribution to our understanding of learning in real-world environments is limited. In recent years, however, portable and wearable brain devices have become more readily available for classroom-based research. Complementing existing education research methods, these emerging technologies could provide information about learning processes that might not be reflected in classroom observations or learners' self-reports. This essay critically evaluates the value added by portable brain technologies in education research and outlines a proposed research agenda, centered around questions related to student engagement, cognitive load, and self-regulation. We also address ethical concerns regarding student privacy and the potential misuse of students' brain data.