It is a perfectly timed operation, Claudette said. She believes the youths take a mid-afternoon train, wait in the underpass tunnel that connects Greenlane and Remuera and when the school kids come past they steal their bikes and hop on the 3.11pm heading south.
"It seems to be this little set up going on.
"They're so crafty. If they see the police are there they won't do it."
It appears the bullying is becoming more serious and escalating to include violence as well as verbal threats.
Claudette said in Monday's incident one of the girls was armed with a knife and the older of the two males, who looked about 18, tried to punch her son in the head after asking him to hand over his bike.
"As he was hopping off the bike the boy swung at him. He had to lunge backwards."
Luckily, the punch "didn't connect".
Her son "was completely shocked" by the altercation, she said.
The robbery had been reported to police and the three girls had been caught walking along Great South Rd with her son's bike. This time they had been too slow for the train.
However, the friend's bike was still missing because the two boys who took it managed to board.
Claudette said the incident had motivated her to take action and she would be contacting the council tomorrow to complain about the events.
"It's gotten now to the point that I'm like 'This is enough'. As parents we need to sort it out."
She said she wanted to see cameras installed at the station and more AT staff patrolling the trains.
"It's purely our transport system that they are taking advantage of."
The school kids were forced to walk through the tunnel because there was "no other way", without an alternative connection between Remuera and Greenlane. She said the tunnel was not visible from the road and there was nowhere that was accessible for parents to pick kids up from, because of the motorway on ramp.
Claudette said she feared for both the safety of the local school kids and of other train and tunnel users.
"It's getting to the point where a child is going to be really hurt."