What's that No.6 Up To?

Headmaster "You were smoking in class boy!"
Pupil "I wasn't sir."
"Not you."
"No sir."
"It wasn't you smoking in class?"
"No sir."
"You know who it was?"
"Yes sir."
"Who was it?"
"I can't tell you that sir."
"Why not?"
"I don't rat sir."
"You're smoking now boy!"
"Yes sir."
"How dare you smoke in my study!"
"I dare sir."
"It will stunt your growth boy!"
"I'm six feet two and a half inches tall now sir, so perhaps I've grown enough!"
"Insolant too eh boy! What is it, a Woodbine?"
"Turkish sir."
"Not No.6?"
"No sir."
"You will take 1,000 lines."
"Yes sir."
"You will write out 1,000 times I must not smoke in the Headmasters study."
"Yes sir. I'll do it behind the back of the Penny Farthing shed in future!"
"You should not be smoking at all boy!"
"Are you going to confiscate my cigarettes sir?"
"Yes boy. Leave them on my desk on your way out."
"Shall I put them with the other confiscated items sir?"
"What?"
"The half bottle of whisky and the well thumbed copy of Parade?"
"Agggggh!"