Do you know of any good websites that teach you how to be a good writer? Or teach reading (grammar, etc)?
Khanacademy is a great website, but they don't have any lessons for learning reading/writing.
I receive pretty decent grades in school and the way I've learned is by reading a lot. I read the entire Terry Brooks series and I believed that it helped my writing sooooo much.
is it available online for free?
No, but they're maybe $7 each and fantastic reads. Also, libraries, man.