When an armed soldier takes a junior class hostage, two rookie teachers are forced to defend their class.

I like the logline and the story seems to be not only fresh, but also very interesting.
I would just add another element at the end of your logline.
Maybe urgency gives your concept another boost.

The awful truth is more compelling than this fiction.? What does this story have to say that rises above the level of mere exploitation and manipulation of an ongoing national tragedy?

As a short, this could work. However, I struggle to see how this premise can be stretched out to a full length feature.