The group of 87 school children had mistakenly been classified as adults during the booking process. It meant they were each assigned the standard weight for an adult of 87 kilogram instead of 32 kilograms for a child.

The miscalculation meant that the Boeing 737 appeared "nose-heavy" during take off, requiring the captain to pull pack on his elevator controls to rotate the aircraft and lift off from the runway at Canberra Airport.

The captain maintained steady pressure on the plane's control column to ensure that the aircraft's tail did not strike the runway during the take-off.

The details of the flight from Canberra to Perth on May 9 are included in a short report by the Australian Transport Safety Bureau released on Wednesday.

The group of school children were accompanied by nine adults, and seated at the back of the Qantas plane. They were on their way home to Perth after a school excursion to Canberra.

A review of the flight found that the final load sheet had overstated the aircraft's take-off weight by about 3.5 to 5 tonnes. Calculating the correct weight of an aircraft is vital for both take-off and landing.

The primary school group made up more than half of the 150 passengers onboard the Qantas flight.

Qantas has advised air-safety investigators that new advice about the procedures for booking large groups of children has been issued to staff.