Globally, many schools are replacing traditional classrooms with innovative flexible learning spaces to improve academic outcomes. Little is known about the effect on classroom behaviour. Students from nine secondary schools (n = 60, M age = 13.2±1.0y) were observed via momentary time sampling for a 30 minute period, in both a traditionally furnished and arranged classroom and a flexible learning space containing a variety of furniture options to accommodate different pedagogical approaches and learning styles. The teaching approaches in both conditions were documented. In traditional classrooms the approach was predominantly teacher-led and in the flexible learning space it was student-centred. Students in flexible learning spaces spent significantly more time in large group settings (d = 0.61, p = 0.001), collaborating (d = 1.33, p = 0.001), interacting with peers (d = 0.88, p = 0.001) and actively engaged (d = 0.50, p = 0.001) than students in traditional classrooms. Students also spent significantly less class time being taught in a whole class setting (d = -0.65, p = 0.001), engaged in teacher-led instruction (d = -0.75, p = 0.001), working individually (d = -0.79, p = 0.001), verbally off-task (d = -0.44, p = 0.016), and using technology (d = -0.26, p = 0.022) than in traditional classrooms. The results suggest that the varied, adaptable nature of flexible learning spaces coupled with the use of student-centred pedagogies, facilitated a higher proportion of class time interacting, collaborating and engaging with the lesson content. This may translate into beneficial learning outcomes in the long-term.