BackgroundComputer use is increasing amongst adolescents and so is the potential for related musculoskeletal pain and postural changes. The cumulative effect of this technology-induced, sedentary lifestyle leads to poor posture, pain, repetitive strain injury and dysfunctional movement patterns.ObjectivesThe purpose of this study was to establish the effect of a computer-related ergonomic intervention for adolescents in a school environment on posture and ergonomic behaviour.MethodsAll Grade 8 learners at two randomly selected private schools in Johannesburg were invited to participate in the study (n = 127). A controlled trial compared an intervention group with a control group. The computer usage questionnaire and rapid upper limb assessment (RULA) were assessed at baseline, 3 and 6 months post-intervention. The intervention consisted of a participatory educational programme. An intention-to-treat analysis was undertaken. Alpha level was set at p = 0.05. Descriptive statistics (frequencies and percentages) and between-group analysis of variance, determined differences in the number of participants in the RULA action levels between groups after the intervention and the comparison of positions and type of computer.ResultsAt 6 months post-intervention, there were no participants in action level (AL) 4 and the number of participants in AL 3 had reduced from 26.2% at baseline to 14.8% in the intervention group (p < 0.001). The control group RULA scores worsened over the period of 6 months. Although the learners were still not in an ’acceptable’ range of postural positions, there was a significant improvement between the pre-intervention and post-intervention stage (p < 0.001).ConclusionThese findings demonstrate the effect of an ergonomic intervention and its sustainability over 6 months.Clinical implicationsThe clinical contribution of this study to our healthcare system is that through the early identification and intervention of the poor ergonomics in a school environment, a positive impact on reducing poor postural behaviour amongst learners can be achieved.