When the terrorists first enter the school and shoot the ceiling, the man with glasses fumbles putting the clip back in the gun. A well trained Colombian terrorist would have no difficulty in reloading a weapon he is so comfortable using.
Luis Cali is told that there is a power failure affecting the whole county (to keep him from seeing the news about his father on TV). However, two scenes later, the lights are on over the sinks and on the ceiling in the bathroom adjoining the school dining room.
When they take Enrique Cali out of his cell the Guards Shackle his hands and feet. When they put the leg irons on him you can see he has shoe laces on. No jail or prison would allow inmates to retain or have shoe laces as they can be used for suicide or as weapons (strangling someone).
When Billy Tepper is being beaten, he's being held at his head, so the lacerations should be vertical (parallel to his spine); when he lifts his shirt later, they're horizontal, as if he were beaten from the side.
In the events leading up to, during and after the final battle scenes, the character Ted's outfit changes several times. In some scenes he is wearing jeans with a brown open shirt and cap and in others he is seen in jeans and a red and white checked shirt.
At the beginning when the woman is pushed out of the window, she flips while falling so that she would land on her back with her head toward the building. When the news camera zooms in on her body, she is lying on her stomach with her head away from the building.
When Snuffy finishes his second fake asthma attack, it cuts to a scene of people looking down at him, Luis Cali can clearly be seen glancing upwards and to the left for a brief moment. He's looking at the director to see if the scene's over, then, he snaps his attention back to Snuffy.