I wouldn't worry about your child's specific reading level unless you suspect that something is a struggle. In my opinion, reading should be about joy, not about being challenged.
We do what ConnectingDots does in letting the children pick out their own books. In early elementary with my daughter it was a real mix. She would have a few thick chapter books about topics that interested her (usually some kind of fantasy), a few graphic novels and some non-fiction about her interest du jour like the weather, different countries. She might even throw a picture book into the mix if something on display caught her eye. I noticed that she naturally picked harder books as her comprehension level went up. If she mistakenly picked a book that was too hard she would usually put it down after a few pages.
