Issues with private diagnosis being accepted by schools and NHS?

Yes, they tried to gaslight me and said the Psyc hadn't sent the assessment, when he had. NHS suck. They are always whining about you using the service, and then when you pay private they don't want to accept the diagnosis! 

My son had a private diagnosis. We was refered originally by the school SENCO. We had an initial assessment by a NHS clinic, then they moved us over to a private clinic. After diagnosis they said they'd forward it to our GP. The school about a year later asked me questions about my son including if there was a diagnosis of Autism. I said there was. I thought they knew this already. They asked me to show proof. I had to forward the report to the SENCO team. My son is 15 and struggles with going to school, he says because the school treat him differently, like he's a baby. I have big issues on a daily basis with my son,  As for the diagnosis, I feel its not been taken seriously. I feel no one, not even the GP is offering appropiate help.