LET me ask you to make a great leap of imagination this morning. I'd like you to picture me, your crusty old Tuesday columnist, as a trendy young schoolteacher.

Yes, it was once true. Twenty-five years ago I taught in a downtown school - it would have made Bash Street Secondary look like the Ecole Super-Duper - in Bolton.

I had a trendy beard in those days, and trendy long hair. I even had a sports jacket with leather patches on the elbows. On my first day in Whitecroft School, I stood at the back of the hall while the headmaster bumbled his way through the assembly.

I felt sorry for him. From the edgy look on his face and the way he paced about on the stage, it was clear that he was not enjoying the experience one bit. So after it was over I volunteered to take the occasional assembly for him.

The headmaster leapt at my offer - I thought he was going to kiss me. But what to say first thing in the morning to 600 youngsters who would really like to be somewhere else? I made a hobby of studying the pop charts and watching the sorts of TV programmes which I imagined they would watch. I talked about love in the lyrics of pop songs. I talked about the late-night horror films and what was on at the pictures. I even learnt to talk with passable intelligence about football - but that bored the girls.

To cut a long story short, I ended up doing it every morning for the next four years. I actually got to enjoy it, but the strain of trying to be relentlessly jolly was wearing. The youngsters seemed to like it. They even laughed at some of my jokes.

One Monday morning at about this time of year I decided to forget all about trying to be the Great Entertainer, and just tell them the story of Holy Week from Palm Sunday when Jesus entered Jerusalem on a donkey, right through to his arrest in the Garden of Gethsemane and the Crucifixion on Good Friday. I told a little bit of the story each day all week.

I told it without frills or extravagant gestures. Just the plain and well-known story. The result was astonishing. They listened as if their lives depended on it - which, of course, they do. I told them about how Jesus threw the money-changers down the steps of the temple; how he ate the Last Supper of bread and wine with his disciples; of his betrayal by Judas Iscariot in the Garden of Gethsemane; of the Cross where he said: "Father forgive them, for they know not what they do."

They listened. Something like awe and reverence and a heartfelt pity descended on the assembled company of blighters. They sang "There is a Green Hill" and "When I Survey the Wondrous Cross on which the Prince of Glory Died." They walked out quietly at the end and, of course, five minutes later, they were back in their incorrigible habits of running along the corridors, whistling when they shouldn't and firing paper pellets.

I should not have been so amazed. People young and old will always respond to something that is deep and true and tender. But that week back in Bolton in the 1970s was one of the most moving and thrilling experiences I've ever lived through.

* Peter Mullen is Rector of St Michael's, Cornhill, in the City of London, and Chaplain to the Stock Exchange.