New diagnosis

Hi, My 8 year old has recently recieved a diagnosis of autism. He was referred to CAMHS for anger issues and low self esteem. He frequently lashes out at his younger sister. He has had a few 121 sessions with CAMHS but has not helped isssues at home or school. School describe him as frequently having meltdowns. We have been told he will be discharged after 1 more appointment. We have tried everything and nothing seems to work and I don’t even know if the diagnosis is correct as referral only happened at Easter. Any advice?