Universal school-based interventions are interventions delivered to all students, irrespective of need, in peer groups. On average these interventions show small, positive, effects. However, a number of recent well powered trials have reported null and iatrogenic (unintended negative) effects from universal school-based Mindfulness, CBT and DBT based interventions. I will discuss these findings and focus on the results of one large universal CBT based intervention from Australia. I will propose a number of potential mechanisms underlying these results, present some possible solutions whilst also discussing whether or not the field should move away from universal school-based interventions.