One of the changes I have made (so far) in rewriting my novel for the 9-12 age group is to move the location of the attack on my protagonist. Originally, the attack took place in a deserted park which always felt slightly wrong. I think the problem was that I couldn't truly picture the park. In the latest draft, the attack has been moved to a derelict street where there is no apparent chance of help. I can see that street in my mind's eye. I can feel the roughness of the torn tarmac under my feet. I can hear the wind whistling through the smashed windows. It feels right.
The Other Side of the Story has an interesting article on the same topic of settings - How your setting can affect your characters - that is well worth a read. Have a look.