....the story is implausible.
I think it unlikely that an extermination camp would have been so lightly enclosed and guarded, which was essential for the essential conceit of the story to work.
However, this does not matter. The stories of many films that convey truths are basically implausible. Slumdog Millionaire is also implausible, but a splendid film about hope, love, family and friendship.
...the Boy in the Striped Pyjamas is about those things, too. It is also about incredible, industrial cruelty, and about evil. True evil, within the living memory of my parents.
...it is a fable, a shocking, and very well made one at that. It would be an ideal way of starting debate with your teens....
I had considered showing it to the more thoughtful of my urchins, but watched it myself first and decided it was best to wait a few years. I found myself crying watching it (I was drunk. This may not have helped) and think it more powerful than other films on the same subject, Schindler's List for example...
(Schindler's Ark was a fine book, though...)
....I await the film of The Book Thief. If done properly, that could be a fine thing....