Although the kohanga reo's car seats were secured that way, they also should have been buckled in by the van's seatbelts threaded through each seat, Plunket child restraint technician Kerri Harnett said.
Ms Harnett said having children unrestrained was simply not good enough. "They should have known, they are carrying other people's children," she said.
"They should be bending over backwards to make sure their vehicle is safe to carry children."
Three young children were in the back and another two were in car seats. The eldest was school-aged.
She would not reveal the name of the kohanga reo involved.
Te Kupenga Hauora is a health body involved in Operation Kiddiclick.
Manager Theresa Wharekura said it could be easy to miss things when other people were involved in loading a vehicle's car seats. "There are a lot of instances where things aren't put in right. There are a lot of things ... to trip up on unless they are doing it all the time."
Tauranga's road safety co-ordinator Lynette Hines said people not restraining their children correctly was one of the biggest issues she faced.
"People think they have the seats in correctly.
"The majority of parents and drivers try hard but about 75 per cent don't get it right," she said.