Issues with private diagnosis being accepted by schools and NHS?

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.

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.