Mestari, ZakariaZakariaMestariPradel, SéverineSéverinePradelVeyre, AlineAlineVeyreSermier Dessemontet, RachelRachelSermier Dessemontet2026-10-052026-10-052026-09-212047-3869https://hdl.handle.net/20.500.12162/15986Background: Children with intellectual and developmental disabilities (IDD) are at higher risk of exhibiting challenging behaviours (CB). Positive behaviour support interventions like the Prevent–Teach–Reinforce (PTR) school-based model, have demonstrated effectiveness in reducing CB and promoting appropriate behaviours (AB) among students with persistent CB in mainstream schools; however, evidence with students who have extensive support needs in special school settings remains limited. Objectives and method: This single-case experimental study with multiple baselines across participants assessed the effects and social validity of the PTR for four students with IDD in special schools. Results: Implementation was associated with overall reductions in CB and increases in AB, although effects for some students were more apparent during the maintenance phase than during the intervention phase. Variability in behaviour and baseline trends were observed, highlighting the importance of multi-source measurement and ongoing monitoring. Teachers were able to implement PTR intervention plans without prior training and reported high treatment acceptability. Conclusion: Findings suggest that implementing PTR for students with IDD, CB, and extensive support needs in special schools is both feasible and promising. Results highlight the value of structured coaching and attention to contextual factors in intervention planning.enType de référence::Article dans une revue scientifique10.1080/20473869.2026.27302372047-3877