"I guess she didn't realise that this was her last stop and everybody was getting off," she said. "The book was just too good."
The driver then left the college and headed for his next job.
By the time he was driving through Wadestown, in the city's western suburbs and about a 10-minute drive from Queen Margaret College, he realised there was still a student on board.
"The bus driver then said, "Oi, what are you doing here?" And he then pulled over to the side or the next bus stop, and just told her to get off, basically he kicked her off the bus.
"He wouldn't let her snap off either. Which, for her, she knows she must snap off otherwise the money runs out on her card."
The girl was ushered off the bus in the middle of an unfamiliar suburb in the pouring rain, with no idea of how to return to school, or how to get home.
Another bus soon stopped when it saw her crying at the side of the road, and told her to cross the road and walk to another bus stop.
But in her panic, the only information that got across was to cross the road.
Crying, sodden, and cold, it was a stranger who came to her aid, something her mother said could have ended badly.
"Thank God this person was a nice stranger and they've given her Poppa a call.
"They've called up her Poppa and explained, look, we've picked up your grandchild who's standing in the middle of Wadestown crying, we're going to drop her to school."
Metlink and NZ Bus, which operates the 621 service, have both said the incident was regrettable.
In an email to the mother they admitted the driver failed on multiple occasions to follow proper protocols.
"We've investigated this case, and met with the driver who confirmed there was one student left behind on his bus," Metlink said in the email.
"He then dropped this student at a stop with the assumption they would catch another bus. We acknowledge that this was not practical, due to the age of the child.
"The correct thing to do in this situation would have been for him to inform comms that a child had inadvertently been left on his bus so arrangements could be made to get her home safely."
The driver also failed to check the bus was empty when he finished the 621 route at Queen Margaret College.
In a brief statement, NZ Bus chief operating officer Jay Zmijewski said appropriate action has been taken with the driver concerned, but he would not say what that action was.
He said further steps have been taken to ensure this type of incident does not happen again.
Metlink general manager Scott Gallacher said the situation was regrettable and rare.
He said he could not comment on what action had been taken against the driver, but did say normal procedure had not been followed.
The mother said she does not think NZ Bus or Metlink have taken the incident seriously.
"I don't think they've done enough, to be honest.
"What they've basically done is said to me as well, we'd like to give you a gift which is a voucher or something for a book or something like that, and I just thought oh God.
"They're just trying to brush this under the rug sort of thing. I'm not going to shut up about it. This could have ended up a lot worse."
Metlink did also offer to refund her daughter's fare for the trip in question, $1.90.
