Primary school children are being warned about possible sex predators trying to trick them with: "Your mum sent me to pick you up."
St Albans School says three incidents have been reported recently where pupils told their parents of being approached by strangers while walking to and from school.
In a fourth incident, a man outside St Albans School was seen acting suspiciously and taking photos.
"Three children, one girl and two boys have been approached in the past couple of months and encouraged to go with men who have said 'we know your parents', 'or your mum sent me to pick you up'," said St Albans School principal Ginnie Warren.
She wouldn't give specific details of what had happened after the children were approached, but said they had "got away".
"After the terrible case in Timaru it has made us very aware that it takes a community to keep our children safe - bad people are out there," said Mrs Warren.
Earlier this last month a nine-year-old Timaru boy was allegedly abducted on his way home from school and was found with head injuries 15km away from the school. A 26-year-old old man has been arrested.
"I would ask parents to be hyper-vigilant and if you feel safe take a photo of the person. Although I don't want parents to over react I'm always over cautious in this situation - it is scary."
Police are investigating.
Senior Sergeant Pete Stills said that earlier in the year they had similar reports from St Albans, Merivale, Bryndwr, Northcote and Casebrook areas about a man acting suspiciously but reports had ceased since they had spoken to a man.
"We believe it was the same man from the description we were given. We spoke to the man, who has a history of this type of behaviour and lives in the area. We continue to monitor his activities."
Senior Sergeant Stills said it was vital parents educate their children not to fall for approaches being made by strangers.
"Make sure your children know that if you cannot make it to pick them up then you will let them know either through the school or contacting them directly. Make sure your children know not to ever fall for that."
Mr Stills said police had spoken to a man in the Elmwood area earlier in the year who was doing "some unusual things".
"There was a guy in a van who lived in the Elmwood area who did some unusual things, hanging around schools, driving slowly past. We spoke to him and monitored his behaviour," he said.
"We did have some stuff reported of adults trying to entice children into a car by offering incentives like sweets or saying 'mum can't pick you up and they sent me'.
"We would encourage parents to sit down and discuss stranger danger with children ... what would they do if someone you didn't know approached you," he said.
Mrs Warren encouraged parents to talk to their children about who was picking them up from school each day.
"We have talked to the community constable and community watch are patrolling more regularly around the school," she said.
The school plans to involve police in teaching their Keeping Ourselves Safe unit in 2013.