I knew it would be a good idea to get some photographic evidence but my phone was in the backseat. We wound down the window and yelled at the boys to leave you alone - I hope you heard us. The bigger one looked up at us with cold flat eyes. He couldn't have cared less that we had seen his cruelty.
"Come on" said the smaller of the thugs. "Let's go" and I could see in the rear view mirror that he'd grabbed you by the arm and was leading you, and your bike, away.
A man waiting for a bus further down the street looked up to see what the noise was and I hope he intervened.
Because we didn't.
"We have to stop," I yelled at my husband.
"Where?" he said frantically, and as I slowed down to stop, the car behind me tooted and we found ourselves caught up in the inexorable flow towards the motorway. We both felt sick. I've never been a witness to bullying. I've stepped in when my girl and her friend were accosted by a couple of street kids and I shouted at a man abusing his wife in the car park across the road and stayed shouting at him til the police arrived. But you don't care about that, do you, sweetheart? You just wanted someone to stop the bullies who were terrorising you on Thursday afternoon and we let you down.
Why didn't you ring the police, asked an acquaintance.
And do you know, the thought never occurred to us. Had it been a grown woman being cuffed around the head and two men standing over her, we would have been on the phone like a shot. So why didn't I call for help when I saw you in trouble? I suppose because I thought, in my arrogance, that I could fix it.
I assumed you were all from the local intermediate school, given your ages and sizes. I discussed with my husband how I was going to make an appointment with the principal, tell him the story and try to help you that way.
Over the weekend, I had mad visions of swooping into a school assembly, like an avenging angel, identifying the two culprits who would break down and confess all and arrange a really amazing day out for you and a friend to let you know that everything would be OK. But that's not how it panned out.
Can you please talk to a teacher you trust and let that teacher know what's going on? Maybe it was nothing but I seriously doubt it. We could see you were upset. And the arrogance of the little shit who was cuffing you was breathtaking.
He looked straight at us and dared us to do something about it. We could have, and should have, done more.
I made the wrong decision by not stopping. You are more important than a line of traffic.
I hope that other people saw you and helped you out. Or that your parents might read this and realise now why you're so sad and withdrawn. I'm sorry. I failed you last Thursday afternoon, but I hope it's not too late to help you now. (That offer of an amazing day out for you and a friend stands.)
You don't have to put up with this and you're not alone.
Kerre McIvor is a host of Newstalk ZB's 'Kerre McIvor and Mark Dye Afternoons'.