In one shot, Aya Ayano screams desperately in shock while her face is covered in blood, a few shots later, Aya is still screaming in her desk. But her face is clean. When she is outside the classroom, crying on Izumi Akazawa's lap, her face is covered in blood again.
When the Professor Kubodera is stabbing himself. There are students in the first row of desks. They appear and disappear between shots.
Many students were spattered with Professor Kubodera's blood, when they flee the classroom, their clothes and faces are clean.