is private assessment accepted by NHS?

hello everyone

I am mother of two years old son. I suspect him having mild autism. We already seen language therapist and she confirmed my suspects and now we are on the waiting list for assessment.  It could take long time. I do not want to wait for too long because with big help on time my son could possible 'growth out' the autism. We started thinking of private assessment. My question is: is private assessment accepted by NHS? What happens after assessment?