My ds is the same year (he's a March birthday though). I admit I'm fairly free and easy about what he reads. From memory these are some ...
Yr 5 - he read among other things the Hunger Games trilogy and the whole Cherub series - I know this is not something everyone would be comfortable with but him and I talked it through and I do believe children self sensor ... also Maggot Moon (again not everyone's thing) and Wonder (dd also read this age 8 ).
Yr 6 - Divergent series, Gone series (he read I think 4 of them but then was bored with them), The Fault In Our Stars, currently on book 3 of Maze Runner books ...
He wanted Gone and that caused the ruckus today. Hmmmm, I'm just not sure, but I do take your point about self censoring, and I must admit I am influenced by the fact that any of these post apocalyptic books would make me feel very depressed, and I worry it will make ds so too.
He also mentione the fault in our stars, is it not terribly upsetting?
Thing 2 is working his way through maze runner. Not sure why thing 1 not so keen.
Will look aMaggot Moon too, thank you.