"I was a high school bully, and I made one girl’s life hell."

I feel two emotions when I acknowledge what I was: Guilt, which is the one everyone expects, and embarrassment, which is the one most people are surprised by.

If you saw me now, a PA for a straight-talking boss in the finance industry, wearing pearls and silk scarves sticking up for the younger recruits in the business, I doubt you’d pick me as a high school bully. There’s nothing about me that suggests tough, or rebellious, or anything really, but fair-minded and, well, nice.

But I was a bully of the first order, and it’s something I’ve been agonising about lately, even though I left school 30 years ago.

Have you seen the movie Flatliners? That’s what brought all this uncomfortable emotion bubbling to the surface. Kevin Bacon’s character David flatlines, and is transported back to grade school, where he bullied a girl called Winnie Hicks. He and his evil little mates dance around her, calling her names, catching her in a childish circle of hate and intimidation.

I watched it again a few weeks ago. And all of a sudden I remembered Caroline and the many times I made her life hell.

We lived in a country town, and started Year 7 as day girls at one of the private schools there. I knew Caroline’s family. Her dad had ‘run off’ as they said back then, though I didn’t know who with. Her mum was a dressmaker, and a good one. God knows how hard she must have worked to pay the school fees, but she managed somehow.

Caroline arrived for our first day of high school in a uniform that was much too big for her – her mum’s attempt to economise, I suppose, knowing Caroline would eventually grow into it.

But instead of being kind – or, at the very least, just ignoring the billowing fabric – I went to great pains to make sure everyone noticed it. Caroline and her outsized school uniform became the butt of joke after joke. That one dress opened so many cruel opportunities says volumes about how determined I was to make Caroline’s life difficult: Hey Caroline, does you mum think you’re going to pork up to fit that dress?

Hey Caroline, your knuckles are dragging along your hemline – what are you, an ape?

Hey Caroline, is your family poor? Do you want us to take up a collection?

Been shopping at Vinnies lately?

And on it went.

I have no idea why I did it. But I was relentless.

The awful thing about all this is that we knew so much about each other’s families in the osmosis-like way people do in country towns. My mum would chat to hers with aimless, comfortable familiarity if they saw each other in the street, both of them unaware one daughter was making the other’s life a nightmare most days. I’d stand silently behind mum, head down. I don’t remember being ashamed of what I might have done at school just an hour before – more appalled that I might be seen in Caroline’s company.

That familiarity meant I knew about her dad when others in our class didn’t, and that Caroline’s mum was alone. There were no other kids from single parent households in our year – it was the 1970s and it was the country.

When it all boils down to it, I think I was just unbearably pleased with myself and my ‘nice’ family and my superior position in the classroom pecking order. So I kept Caroline’s absent dad up my sleeve for a slow day.

Caroline came to school one day in, I think, year 8. By then, she’d endured a year of bullying, not just at my hand but – thanks to my lead – by most other girls in the class as well. I don’t know why she was my particular target – there were certainly other girls we considered to be ‘dags’ who copped a bit as well, but nothing like poor Caroline.

I overheard her telling one of her friends that her dad was really famous and that’s why he wasn’t coming to sports day.

And what did I do?

I started to scoff, then laugh, then roll my eyes extravagantly until I had everyone’s attention. Then I said probably the worst thing I’ve ever said to anyone in my life: “Your dad isn’t famous and he left your mum because he couldn’t stand being with you.

“No one wants to be with you, that’s why you don’t have any friends.”

You’d think even my teen-addled brain would have realised that was a bullying remark too far, but I didn’t. Instead, we all laughed and squealed loudly about who she’d run with in the father-daughter race (I think I might even have yelled out the window to the groundkeeper to see if he was up for it).

And Caroline ran out of the room in tears. She didn’t come back for the rest of the week. When she did, she was small and subdued.I was given a detention, which only served to increase my ‘legend’ status.

In Flatliners, Kevin Bacon’s haunted character goes looking for Winnie Hicks, and finds her living an idyllic life, married with a daughter of her own. She’s grown strong and left the past behind. In true Hollywood style, Bacon repents and Winnie forgives him.

But real life isn’t always so neat. A girl I work with pushed one of her high school classmates so hard against the lockers she bruised. She actually hurt her physically. My colleague’s guilt didn’t emerge until she had a child of her own, and that sparked a long mission to find the girl she brutalised so she could apologise. She hasn’t been able to.

And I know I wasn’t the worst bully in the world, even though I feel like I was definitely up there. Seniors at the boys schools near mine were masters of the art, making younger boys run until they’d vomit or forcing them to stand outside on cold nights in bare feet. I know one boy – a fantastic cricketer – who was on the cusp of selection for zone or state who was bashed so badly by two older boys he couldn’t play in the critical game – or for several more afterwards.

He saw his tormenters at his 20-year school reunion. “G’day mate,” one of them said. “What have you been up to?”

He punched him so hard he broke his nose, then decked his other tormentor as well. “That’s for what you did to me at school,” he said before striding off as his classmates looked on, gobsmacked.

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Caroline left our school in Year 10. The bullying might have eased up by then, but I’m not really sure – it was of so little consequence to me I simply can’t remember.

I feel guilty to the point of nausea about Caroline, but mostly I feel sick with embarrassment that I could have been so cruel. It’s completely at odds with the person I am today – but what difference does that make? I can stand up for the underdog in 2015, but god knows what damage I did all those years ago.

I’d like to find Caroline and tell her how sorry I am and how much I’ve changed. Of course, in my imagining of that meeting, bygones are bygones and we grab a glass of wine together and chat amicably about the good old days.

But in truth, I wouldn’t blame her if she threw the wine in my face.

I think I would.

Did you experience bullying at school?