This study focuses on exploring teacher learning in terms of teachers' professional agency embedded in the classroom. Teachers' sense of professional agency is related to perceiving instruction as a bidirectional process, use of students as a resource for professional learning and continuous reflection on teaching practices. Accordingly, the capacity to cross the boundaries in teacher learning contributes active professional agency and, consequently to work-related well-being. Hence, the interrelations between teachers' sense of professional agency and the burnout they experienced were also analysed. Altogether 2310 Finnish comprehensive school teachers, including primary, subject and special education teachers, completed the study survey. The results indicated that active professional agency, promoting both learning and well-being, requires not just reflecting and adapting but also efforts to learn at work. Moreover this requires not just self-directed and active professional practice but also learning at the boundaries and creating new professional knowledge together with students and colleagues.