I am trying to establish reasons for why you took this job on 7 months ago, why the parents felt the need to have a nanny rather than other forms of care, plus seeing if the child may have special needs (if he was on a special diet, combined with how you describe his interests and lack of bonding, it may have been an indicator to Autism).
As a nanny, I would not apply for a job caring just for a 9 year old. I expect I am like many other nannies, in that I mostly work with children under the age of 5. Therefore I am trying to establish why it is that you did apply for this job... given your level of previous experience.
"they need somone to collect their son from school make the tea etc?"
So why are you trying to do lots of things with him? You are mostly there to stop him wrecking the home, injuring himself, making him tea, trying to get him to do homework... aren't you?
You are not happy there, so leave. Does not sound like you want to try to fix things and it doesn't sound as though trying to fix things will actually help - as you won't fix the parents attitude.
Be prepared though for your next employer to ask you about the job, about why it is that you decided to leave after 7 months... rather than say within the first 2 months. A future employer may be wondering the same thing I am... why you would apply for that job in the first place and not work with younger children.