Following our longitudinal study of teacher burnout and digital fatigue, this paper examines boundary-management strategies used by 312 teachers in Finland and Sweden working in hybrid schools that combine on-site and remote instruction. Hybrid provision has persisted in Nordic secondary education beyond the pandemic period, and with it the expectation that teachers remain reachable through learning platforms, messaging applications and email across the working day and beyond. Drawing on boundary theory and the job demands–resources model, the study investigated which strategies teachers use to manage the boundary between work and non-work in digital environments and whether those strategies are associated with lower digital fatigue and higher wellbeing. A cross-sectional survey administered in spring 2026 measured five boundary-management strategies, digital fatigue, emotional exhaustion, work engagement and perceived school-level communication norms. Hierarchical regression analyses controlling for age, teaching load and hybrid intensity showed that teachers who apply strict notification limits and scheduled asynchronous communication report significantly lower digital fatigue than teachers who do not, with standardised coefficients of −0.31 and −0.24 respectively. Physical separation of devices had a smaller effect, and mental detachment routines were effective only when supported by school-level norms. The effects of individual strategies were moderated by the extent to which schools had explicit communication norms, with individual strategies contributing less where norms were strong. The findings indicate that boundary management is a shared organisational responsibility rather than an individual coping skill, and they offer guidance for school leaders seeking to protect teacher wellbeing in hybrid settings.