Sydney - Identical triplets scored identical grades in their final year at an Australian high school and were each awarded prizes for top achievement.

"It's nice coming out equal because we always get asked who's the smartest," Kate Stevenson, flanked by sisters Amy and Lisa, said Friday.

"It was something we all were hoping for when the prizes came out and we got three each," she told Australia's AAP news agency.

Never before in the 50-year history of Brisbane's Wavell State High School had the award for the top student in the graduating class been split.

"My maths teacher said, on the law of probabilities, it was pretty much impossible all three of us could get such a close result in our marking," Kate Stevenson said.

Principal Jeff Major said that even with a count-back it had proved impossible to pick a single winner. "We tried our hardest to separate them but just couldn't do it," he said.

Tom Stevenson said a three-way tie was the best possible result for his daughters.

"We knew all three of them would do well, but equal first is absolutely amazing," he said. "For this to happen in the final year is so wonderful for the girls because none of them will feel any less special than the other."

Next year, the girls are to start degree courses at separate universities.