Autistic Child Falling Rapidly Behind At School


I have a 6 year old son who has been diagnosed with autism and has an EHCP in place. He goes to a mainstream school. 

The support the school have accessed through the EHCP seems to focus on managing and preventing his 'meltdowns', but there seems to be little effort made to actually teach him. Other students his age are spelling words such as 'annoyed' whereas my son cannot spell three letter words. 

He's a very intelligent and imaginative little boy, but unfortunately the school lack the ability to handle his condition; I do have sympathy with this, they try their best and his teachers love my son.

My question is, what next? 

Do I accept that my son cannot learn given his current setup, or are there support services available around education? 

We're at a desperate and emotional stage and just want him to have a good life; we already feel like we're failing him and he's only 6 

Thanks in advance.