The Scots College has failed in its legal bid to expand its preparatory school in Bellevue Hill in Sydney’s east due to the “risky and/or illegal” conduct of parents while dropping off or collecting their children.

The school launched the court challenge earlier this year after Woollahra Council failed to meet a deadline to determine whether it could convert a house in Kambala Road into an 80-student early learning centre.

The council nonetheless rejected the application in June on planning grounds, particularly due to a requirement for an on-site drop-off and pick-up area.

But the NSW Land and Environment Court found the council’s planning controls provided no basis to refuse the application. However, the conduct of the school’s parents did.

Senior Commissioner Tim Moore concluded that he was not satisfied that there would be no increased safety risk, “given the present dangerous parental activities”, if the application was approved.

“A significant number of parents dropping off and/or picking up children from the preparatory school pay no regard to the law, child safety or the instructions given by the preparatory school,” said the judgment, which based its assessment on evidence from nearby residents, including photos, and the preparatory school’s “own limited traffic survey”.

The commissioner noted that the consequences of a car colliding with someone – particularly a very young child – were “potentially catastrophic”.

“Any increase in risk to young children because of risky and/or illegal behaviours (ones regularly warned about and counselled against by the preparatory school and the college) is completely unacceptable.”

This week’s ruling is a serious blow for the college, which has taken the council to court in a separate bid to increase the number of students covered by an enrolment cap at its nearby Victoria Road campus by 350 pupils. That matter resumes on Monday.

The school’s growth has also prompted legal action by residents’ group, Concerned Scots Neighbours, which welcomed Mr Moore’s decision.

“This judgment goes to the heart of the duty of care that a school has – not only for their students inside their grounds, but as they arrive and leave,” the group’s spokesman Paul Blanket said.

“For a reputable school like Scots to have a judgment that calls into question their attitude to the safety of their students, it is very worrying.”

Scots College principal Ian Lambert, who said “the safety and wellbeing of our boys is always our primary concern”, described the judgment as “extremely disappointing on a number of levels”.

“At the suggestion of Woollahra Council, the college included improvements to the drop-off and pick up zone on Kambala Road in its application,” Dr Lambert said.

“It is undeniable that this improvement – at no cost to ratepayers – would have improved the safety and amenity of students and local residents.

“In practical terms, this decision means that the current situation continues without the prospect of the improvements to safety and amenity we had desired.”

Dr Lambert said the school would carefully consider the judgment “before making any further decisions”.

Woollahra Council said it was awaiting an analysis of the judgment before making any comment.