I Survived: The Attacks of September 11, 2001 by Lauren Tarshis. Scholastic, 2012, 82 pages.

Great series--realistic disaster historic fiction- famous disasters through out history are the background for stories about a child who lived through the disaster--no children are harmed--
-- Also the kids have a back story too.
Lucas's Dad and Uncle are NYC firefighters. Lucas get especially close to his uncle when his dad gets hurt on the job. Lucas loves football, just like his uncle, but gets a concussion, and when his parents tell him no more football, he goes to NYC to find the Uncle at the firestation to ask him to intervene.
Realistic without being too graphic--end pages provide more history. Light over all. A winner with younger and middle grade readers. 3rd and 4th i would think.