I just don't understand...

- I have 13 students enrolled in my period 4 class. Then how come only four showed up to class today? I just don't understand!

- I have 3 new students coming into my period 7 class today. They are all related and did not go to any other school this year. All of a sudden, they just decided that it was the right time for them to register and ruin the nice, neat order I have in my class. Where the hell were they when school started? Do they think they could just show up when they want to? I just don't understand!

- I have a student in one of my classes and everytime I assign something, he yells, "No teacher, no..." like I'm performing some torturous act on him. I just don't understand!