During my years as a teacher, I never ceased to be amazed at the pupils' imagination, wit, and exemplary behaviour.
One of the most astonishing reversals of behaviour, in myself and a pupil, occurred some years ago when I was class tutor for 4 years.  This entailed checking the attendance, before and after school, for 10-15 minutes, and to be there for the pupils if they had any home or school issues they wished to discuss.
One girl in the class, Ayesha, was highly intelligent and seriously arrogant.  From years 8-11 she took little notice of me, and would frequently visit her friends in other classes during registration.  She was never openly rude to me, but she carried on as if I wasn't there.  I did have discussions with her and the head of year, but little dented her wilful disposition, not even detentions or talking with her parents.
Towards the end of their last school term, Ayesha asked me if she could be excused during registration to visit her friend who was upset after a row with another friend.
I turned to her and slipped out of character in terms of what I said, replying in a calm way, concealing my inner rage:
"Why are you bothering to ask my permission to leave the room?  You never have before, in fact you haven't taken the slightest notice of me in 4 years.  You just do as you please, regardless of what I say.  So, since you obviously have no respect for me, I now have no respect for you.  Don't ask permission, just do as you've always done - do what you like.". 
Ayesha looked stunned as I turned to deal with another pupil.  Ayesha went back to her desk and sat down. We barely spoke during the last 2 weeks.
At the final assembly for year 11, a representative from each class spoke for the class, reviewing their years at the school and then saying 'Thank you' to the form tutor.  I was surprised when Ayesha stepped up to the microphone.  I half-expected her to assassinate my character and tell the school how I murdered her self-confidence by telling her I had no respect for her, which, in the cold light of the assembly hall, would sound like an atrocious thing for a teacher to say to a pupil.
She talked about her experiences at the school in an engaging way.  Then she turned to me.  She just looked at me for what seemed an age.  She told the story of how she had treated me for years and repeated what I said to her 2 weeks ago.  She added:
"I want to thank you, Mr.Nance, for putting up with me for so long.  What you said to me 2 weeks ago was the best thing you could have said.  It made me realise how arrogant and disrespectful I have been, especially to you.  So thank you for being such a tolerant tutor, such a good guy!"
Only shock prevented me from crying.
I am pleased to say that over the next few years, Ayesha used to occasionally visit the school, just to say 'Hi!'