"Nothing untoward happened but the mere fact they got into a stranger's van is a concern. My understanding is the matter was reported to police by my staff.
"It's just odd that a stranger will pick up children and drop them off. It's kind of an invasion of privacy or grooming. That's not normal behaviour by someone who doesn't know the children he's approaching," Mr Van Rijswijk said.
The school has sent out safety messages through its newsletters and the principal said parents should again talk to their children about not accepting rides from strangers.
Morningside School principal, David Prchal, said police have advised his staff about a driver who offered children a ride home after school.
A black ute and a white van were seen after school last week, he said.
Mr Prchal said his staff were informed that on October 19, the driver picked up two children and drove them to a Morningside house but it was not known which school the students attended.
A day later, teachers spoke to all students and reminded them they should never accept a ride from anyone other than a family member or a person they knew who was supposed to transport them home.
"It's a timely message for students as well as parents. My approach to a situation like this is to make sure we get the information out there without creating panic or concern," Mr Prchal said.
He said the student safety alert on the school's facebook page last week had an astonishing 30,000 views.
The school has a roll of 315 students.
Whangarei police school community officer, Senior Constable Ian Anderson, has not heard about the latest incidents but urged anyone concerned about the behaviour of people outside schools to contact police immediately.
Mr Anderson visits schools around Whangarei under the "Keeping Ourselves Safe Programme" to teach students about dangers strangers pose and the safe use of social media and electronic devices.
"By knowing what they should and shouldn't do not only keeps students safe but others as well. We'd urge people to note vehicle registration numbers and pass them on to us."
He said cases of strangers approaching students outside schools have been rare although there were two cases last year and another a few years ago.
"There are cases where children have certainly taken safety messages on board but it's worrying that there are people out there who we need to identify and stop," Mr Anderson said.
Te Tai Tokerau Principals' Association president, Pat Newman, said schools in Whangarei have successfully conveyed safety messages to students which was why children have managed to stay safe so far.
He said there could be any number of reasons strangers would approach children outside school, including estranged parents who wanted to interact with students.
The Hora Hora Primary School principal said his students have not been approached but they have been spoken to about the dangers of approaches made by strangers.
In April 2011, a man followed a 17-year-old student of Whangarei Girls' High School and demanded she get in the car with him.
She managed to flag down a passing female motorist who drove her home.
