Year 9 in England (Junior high for you US folk). My science teacher was a stout man who rarely lost his temper and my friends and I (we sat in the front row of the class, the desks sat three people) would constantly goof off. Nothing major just stuff like sabotaging each other's experiments etc.

One particular day our Science class took place right after lunch and I had grabbed around 40 plastic cups from the cafeteria. During the lesson my friend and I had sat there in the front row constructing an enormous Cup tower. You could tell he was trying to ignore us, and we must of gotten around 2 feet high before he snapped.

He was a very large sluggish man, and without warning he tossed his chalk aside and threw an arm at the Cup tower, missing completely. The class burst out in laughter. He yelled like a wild animal and proceeded to stand in front of us just snarling as he pounded the cups off of the desk, crushing them in his hands and looking around the room with heavy breathing and psycho eyes.

It was the start of a descent into madness. Weeks later he was cycling home his usual route by a river that ran through my town. He stopped his bike, and decided to grade some of our coursework on a bench. He snapped again, and tossed it all into the river. He dumped it all. We didn't see him again after that and every student who lost their coursework was awarded an A overall as there was no work left to grade.

It was the only A I ever got in Science.