How I discovered Harry Potter and a question

[Sofie]

This is the tale about how i found the wonderful world of Harry 
Potter. My step-father/ mother's boyfriend writes History non-fiction 
books. Occasionally he gets freebie's form his publisher, one of 
which was Harry Potter and the Philosopher's stone. He dismissed it 
as a children's book and past it on to me. I was slightly insulted by 
the idea that at fourteen I was a child so I put it on my bookshelf 
and didn't look at it again for a while. But then I got ill. I reda 
everything on my bookcase and then I came to PP, so I read it. Loved 
it and sent my step-dad out for book 2. And then a few months later 
PoA came out. By thren i was hooked. I bought GoF the day it came out 
for £10. I'd read it in 4 hours. By then my friends' were also 
hooked (through my constant talking about the books) and a couple of 
weeks ago we all went to see the film. 

My question is, how old are people in ninth grade? I know some of you 
are American and teachers at that, so I was hoping you could answer 
my question for me. Thanks!
Sofie