A school community in Sydney's northwest is doing "remarkably well" after a pupil's mother was hit by a bus carrying students returning from a school camp.

The 38-year-old woman, who has not yet been named, was struck and killed at the intersection of Hannah and Beecroft roads at Beecroft shortly after 3pm (AEST) on Wednesday.

She was carrying her 11-month-old baby girl, who was thrown from her arms and escaped injury.

A regional director at the NSW Department of Education, Jane Simmons, said the school was providing counselling for staff and students who were doing "remarkably well under the circumstances".

"Some children will want to talk about it, some children will not want to talk about it, some children will cry," Ms Simmons told Fairfax Radio on Thursday.

"There are all sorts of different behaviours and reactions and we just need to be cognisant of those ... not just today but over the next few weeks as well."

The bus which hit the mother was packed with students from Beecroft Primary School returning from an excursion.

Among them was the woman's older daughter, police duty officer Darren Jameson said.

"Fortunately, she didn't see the incident but she was on the bus," he told Macquarie Radio.

"It's a tragic day, not only for the family but for the witnesses and the bystanders."

Ms Simmons said staff at Beecroft Primary would be working closely with the family to prepare for when the older daughter returns to school.

Police have interviewed the 69-year-old bus driver, who was taken to hospital for mandatory blood and urine tests.

The bus has been seized for forensic examinations.

Crash investigators have renewed their appeal for witnesses to come forward.