for further information see guidance on commissioning targeted mental health and emotional wellbeing services in schools department for education a and me and my school department for education b the tier system describes the services that should be available at different levels of need responding to different complexities of demand but both the affected child or adolescent and the camhs teams should be able to move between these tiers so that the most appropriate services are accessed and delivered support from an early intervention team is for a limited amount of time usually three years