Monster House is definitely not for children under 12 years!
There are points in the film, the one she would have played with real actors, 1: 1 could be found in adult-horror movies.
I asked my son after a few minutes if we prefer to look at something else. But he was "courageous" and wanted to look. Papa sat with mixed feelings next!
But after 5 minutes when the children in the house were then (and I my partner a horrified "as crass !!" threw), and a cast-corpse found, then my son said, "Dad, I do not want to see the"
I, too, would now eh canceled the look of the film at the latest!
For children over 12 may be quite interesting (as an introduction to the horror genre because funny is the film sometimes not) but FSK 6 - never!