Has he been determined eligible for special education services or a 504 service agreement at school? if so, use the evaluation report to seek outside agency help or “wrap around” supports. The school may be bale to offer ideas especially since they see him in a different context. The school psychologist and/or school counselors may be bale to help with ideas too. They may even have a behavior specialist you could have a meeting with along with the school team. It takes a village to help our children- seek the school out and/or any community resources in your area like behavioral health or a pirate psych with specialty in ADHD.
Do you have a local chapter of CHADD you could reach out to for some guidance in your area?
I’d also gently suggest seeking a DBT therapist (dialectical behavior therapist) as he/she would combine mindfulness with cognitive behavior therapy- the reframing of your thoughts/views.
PLEASE know that YOU are highly valued. You are given this life as a gift for some reason/s. You need to find supports who can help you on your journey to experience a high quality life as intended by a higher power (if you so believe)