Advice about diagnosis

I went through the private route to have my 6 year old son assessed and he masks. He is awaiting nhs assessment too. The assessment has come back saying there is definite issues but because nothing was picked up at school and he was observed to be ok/ school report said was fine a diagnosis was not able to be made. They said he needs to display these issues in 2 different settings. At home and even in public settings his behaviour is challenging and life is very difficult. Wondering if anyone else had any experience? Feeling frustrated. Thanks