11 yrs. old is a little more mature than 9 yrs. old, and having 'backup' available makes all the difference.
It doesn't say in the story whether or not the parents actually had someone available for contact in case of an emergency, or if there was a neighbor who was willing to stop by to check on the kids. One of the neighbors mentioned that the place they lived was safe, but accidents can also happen, and kids that young, without the benefit of of someone to call, can make a situation worse because of poor judgement.
We had chores and responsibilities when we were kids. I raised rabbits to kill and sell from the time I was 8.
Dad showed me how to slaughter and dress them.
Turned out that I didn't have enough strength in my 8 year old hands to twist the head, so he scrounged me up a length of pipe to 'stun' them with.
That worked. I made money on rabbits until I could push a lawn mower.
Today, he'd be in jail, and I'd be living with a gay couple posing as a 'foster family'.
/johnny