This is actually a Mexican film. The biggest criticism, apparently, is that they didn't use the correct dialect of Spanish. Since I speak little Spanish, doesn't bother me.
I was surprised that the film only lasts about 1hr 30m. It moves extremely fast. Expect no filler material, there's lots of bullets, explosions, and screaming. It wasn't an overly violent film, yet still managers to be shocking, due to children being involved, and portraying something that did actually happen back in 1980.
The film reminded me of Machuca that I watched earlier last year. It's difficult to portray the nature of this film, and steer clear of falling into the war film genre. As it progresses, despite cutting a lot of film making/story telling corners, you'll find it manages to balance the amount of violence and emotion, without treading on clichéd ground. Trying to analyse how good of a film this is due to the history behind the story it is is extremely challenging. As a film with a message, this was powerful, yet it's hard not to be. There's no explanation what the war was about, or the politics behind it, or even the people involved. The rest of things are also kept to a conserved amount. This allows it to concentrate more on the message, but may also be seen as missing out on key factors, that could have made the film have an even greater impact. It's debatable, but at the end of the day, it does feel irrelevant.
Regardless of film standards and critique, this kept me from blinking for 90mins, and most definitely invoked emotion and remorse.
See for yourself.