SYDNEY, June 19 - Ada, who's in Year 12 at Sydney Girls High School, is one of 27 Aussie students prepping and packing before they test their skills against 2,000 of the world's top students in biology, chemistry, earth science, informatics, mathematics, and physics.

The 27 students succeeded against a pool of more than 25,000 applicants in extension programs and qualifying exams across the country to make it to the final cut for the UNESCO International Science and Mathematical Olympiads. 

While Ada's Chemistry Olympiads is taking place in Thailand in mid-July, the other competitions are spread around the world over a six-week period: Biology in England; Earth Science in France; Informatics in Iran; Mathematics in Brazil; and Physics in Indonesia.

She says she is feeling a mix of nerves and excitement ahead of the tough competition in July. 

"It's very stressful, and it's been challenging balancing everything this year, but I'm working hard and up for the challenge," Ada said.

The Aussie team looks even more official now that they've received official Australian team blazers from the federal Industry, Innovation and Science Minister, Arthur Sinodinos, at a ceremony at Parliament House in Canberra on Monday.

Ada's also waving the flag for girls studying and succeeding in STEM (Science, technology, engineering and mathematics).

Almost half of the science students putting their skills to the test for Australia are females - equalling 2015's highest representation of girls since Australia first began competing in the Olympiad. 

Girls will compete in biology, chemistry, physics and Earth science.

Advocacy director for the Olympiads Ruth Carr said the Olympiads were an opportunity for students who often coast through their high school curriculum to be exposed to more challenging concepts, and be pushed further than they had been before. 

"Many students realise through the Olympiads that they really do have a strong passion and love for science."