One of my new colleagues recently expressed surprise that the rest of us were having so much trouble with Angel. "Oh, he always behaves so well for me" he said, smugly. "I didn't even realise he was supposed to be difficult."

Those of us who have taught Angel for the last two years rolled our eyes and exchanged contemptuous glances. Well done, rookie: you got fooled. In terms of Angel and his behaviour, this is simply stage one, and we've all been there: thinking he was no trouble to us, or even that we would be the teacher to "save him", to show him how great he is, to lead him away from the trajectory that so many poor brown and black kids across America follow, the one that starts with missing school and leads eventually to being jailed for something no white kid would ever go to prison for.

You have entered stage two when Angel responds well to your praise of his great behaviour in class and you let him know how smart he is. The unspoken bit of this is: "Thank you, Angel, because by behaving well for me you are showing all my numbnuts colleagues that I am a better teacher, human being even, than them."

Stage three is tough: as soon as there seems to be a connection, a relationship, some emotional investment on your part, Angel will decide the time has come to punish you. You will be standing in for every person who has ever got close to him and hurt him: the mother who abandoned him when he was small, but not before beating the crap out of him every day, the "uncle" who abused him, the kids who can't stand him because his behaviour is so disturbed, the teachers who gave up and passed him along.

But you will also be standing in for you, for daring to have some expectation that he might succeed at something. To Angel, this is nonsense, for in his own estimation, he is utterly unlovable, a total failure, something which he will work hard at proving by coming to class late, cutting class, cursing, shouting, wandering around your room, yelling, "Your sister can lick my balls," at the one guy in the class who will punch him in the face for even mentioning his sister's name, bother other students, bother you, turn one pair of scissors into two knives, throw paper, throw furniture. He still holds the record in my class for the most detentions in one lesson (four, in two minutes, every one a doozy).

Stage four is the exhausting realisation that you can't save, or even do much to help Angel. When a child is subjected to serious and repeated abuse they hide away everything that makes them vulnerable and become a monster created by the adults who should have nurtured them. So, as if being hurt and betrayed weren't enough, they also become a person who nobody can deal with or really stand to be around. They become even more isolated.

Angel's monstrosity is the only thing still available for him to draw on. Any other parts of him; humour, kindness, compassion were long since buried during the struggle to keep going. He's out of bed and dressed – what more do you want?

A week ago I had my last lesson with Angel. He's a ferociously talented artist, a fact I've pointed out to him several times over the last two years, which he's responded to with indifference. When asked to choose his subjects for next year, I expected him to put art at the top of his list and was dreading the prospect of another two years of disruption while conceding in my own mind that it might be the only thing that would keep him in school and might even "save him".

So I was surprised to see that he had put it absolutely last, and was even rather hurt, something he no doubt intended. Consequently, I knew that the final lesson of tenth grade would be my last encounter as an art teacher with probably the most naturally talented child in the school.

At the end of the lesson, after the usual disruption, obscenities and low-level interference with other kids, he asked me to sign his behaviour sheet. I wrote: "Shouted 'suck my dick' at Deon then threw a pencil at his head." Listening to him arguing with me that he did no such thing and that the remark was a quotation/taken out of context/misheard, I was overcome with weariness. "Angel," I said sadly "this is our last lesson together, and honestly, I am done". The fight went out of him, he folded up his sheet, walked to the door and said "OK, miss, have a nice life."

I saw him a few days later from an upstairs window. He was standing, watching, as a younger boy, Charlie, was being punched and kicked on the ground by Deon. I saw this while invigilating an exam, so it was impossible even to bang on the window and yell at them to stop. The noiseless background gave it a strange, dreamlike quality, especially as Charlie put up no fight at all and simply curled up on the tarmac and waited for the beating to end. When it did, Angel approached the boy with his hand outstretched and helped him up as if there should be no hard feelings, like he was saying: "See? It's really not so bad having the crap kicked out of you, is it?" Then all three boys walked off together.

"OK, miss, have a nice life." I do have a nice life: I have a great job, friends and a family I love, who love me back. I've never been punched, kicked or bitten by anyone, much less by someone who was supposed to care about me. I've never been sexually abused, locked in a cupboard, put out on the street in the dark, in the rain, gone without food, had a cigarette put out on my arm. Thanks, Angel, for hoping that none of that happens to me. I wish none of it had happened to you.

Anna Bailey is a British art teacher who works at a high school in the Bronx, New York. This is the sixth of a series: Brit in the Bronx. She writes under a pseudonym.