Deliberate "mistake": When the teacher walks over the floor towards the blackboard, he walks through a lot of blood. However when it cuts, he leaves no traces of blood where he steps.

Revealing: When Shuya impales a commando with a pipe, the strap holding the pipe in place is visible, when he turns towards the camera.

Continuity: When all the kids are locked in the cage you see them running towards the cage hitting it. When it cuts they are running towards it and hitting it again.

Deliberate "mistake": The time taken by the countdown on the exploding collars varies wildly according to what is happening at the time.

Continuity: When Shintaro is shot in his leg you see him lying on the football and there is no blood on the ball. Then it cuts for a brief second to another kid, then back and now the ball is suddenly covered in blood.

Visible crew/equipment: During the gunfight between the terrorists and the students, in the rundown building, a cable can be seen supporting Kurosawa.