I have taught this novel for 8 years. This film's glaring error is to ignore and often to reverse the harrowing moral message of the original novel.
The original locates the capacity for evil within all of us and portrays civilization as a fragile surface beneath which lurks 'the darkness of man's heart'. Golding chose public schoolboys to be isolated on his island so the very 'pinnacle' of innocence and civilization was subverted when they turned to murder, sacrifice, and idolatry.
In this disastrous adaptation, there is a simplistic divide of the boys into 'good guys' who remain untainted by evil and 'bad guys' Moreover, the boys start as military cadets; when they turn to hunting it hardly surprises us. Jack, instead of changing from Head Chorister to The Chief of a tribe of savages, starts off as a delinquent and becomes...a delinquent. The character development is therefore omitted. The moral message becomes a conservative reinforcement of a good/evil division between people.
Golding would be mortified by this travesty of a film.