Canterbury principals say some pupils are being dropped off at school too early for supervision, putting them at risk of accidents.
One principal has reported that unsupervised children were found playing "chicken" with cars.
David Taylor of Canterbury Primary Principals Association says schools are responsible for pupils once they enter a designated school bus or school grounds.
Mr Taylor says most provide supervision from about 8.30am, but some children are arriving as early as 7.40am and this is unsafe because they end up playing alone and unsupervised.
