"Police were notified this morning of a suspicious approach made to a young person on Hastings Rd while that young person was on their way to school," she said.
The concerned mum asked people to share the Facebook post widely in a bid to catch those behind the snatch attempt.
She told the Herald she wasn't taking any chances, choosing to drop off her boy at school this morning.
She said police would be watching the area closely this week.
"We don't want to wrap our kids in cotton wool, but please use [my son's] experience to remind your kids about staying safe and make sure they have a plan if God forbid it happened."
The car was a silver BMW 7 series. Her son, a "car fanatic", thought it was a 2006/7 model. He said a man was driving with a female passenger.
"He's very practically minded but he's also a cautious boy. He heard the car coming and turned to look at it. The moment when they started to open the door he just took off," said Prendergast.
St John's School principal Vicki Trainor said the young pupil acted courageously and responsibly running to school seeking help from a senior teacher.
"We're just very very proud of our little boy, " said Trainor, who praised him for following instructions learned at school on keeping safe.
She said the entire school community had been notified about the attempted abduction through various media options and warned to increase vigilance coming to and from school.
Trainor said the child, a senior pupil at the primary school, had acted "incredibly responsibly" and was able to give police a good account of the harrowing ordeal.
She said police were superb coming promptly to the school once the boy sought help from a teacher.
