Common Sense Note
Parents need to know that characters swear explicitly during combat (not outside of it, though), and there is brief but bloody battlefield violence and fatalities. The younger Kiplings are shown sneaking cigarettes and alcohol unsupervised. Early readers who have come to idolize actor Daniel Radcliffe for his incarnation of Harry Potter should know this is a likeable but very different character he plays, who comes to a very different, sadder end. Viewers whose knowledge of English history and culture doesn't go much deeper than Hogwarts may feel left out.
A naked Jack has a physical, but nothing explicit shown.
Brief but vivid shooting; explosions in the trenches of WWI, with blood gushing out of bullet wounds.
The F-word and Christ's name in vain under battle stress. "Ass," "hell" and "damn."
Good manners, courageous bearing, and being a valiant warrior for king and country are the themes here, even if you wonder whether the filmmakers are endorsing the once-noble ideals of the British Empire or condemning them as having inspired the war that stained the Kipling household (and so many others) with loss. John is an unspoiled young man, and has no problem earning the friendship of the Irish volunteers he commands.
Viewers may be inclined to read Rudyard Kipling books (or see the movie versions).
Drugs / Tobacco /
The younger Kiplings smoke and drink unsupervised.