Set before she was born and unassailable for 24 years, Albury High School’s Sienna Toohey has scuttled the Australian 15-years 100m women’s breaststroke record.

Toohey finished third in the final of the event at the Australian Olympic Swimming Trials, narrowly missing out on the gold medal and a place in the team heading to Paris next month.

In a gutsy swim on Tuesday, the 15-year-old smashed the record Leisel Jones set at the 2000 Sydney Olympics.

Jones won Olympic silver with that swim but would wait another eight years before she finally claimed gold in her pet event.

Standing just 162cm, Sienna made a giant start and held on stubbornly to her lead through the turn but was pipped on the wall by older swimmers Jenna Strauch (first in 1.06.90) and Ella Ramsay (second in 1.06.94).

The buzz about Sienna’s fast start and blistering time of 1.07.01 was as loud as the screams of her classmates who stayed up to watch her race.

None of them, however, could drown out Albury High relieving principal Damian Toohey.

Mr Toohey also happens to be Sienna’s father and was on the edge of his seat watching the race at home with Sienna’s brothers Archie, 17, and Jed, 12.

“We were screaming at the TV,” Mr Toohey said.

“At the 70-metre mark we thought we might be packing for Paris, but we knew the girls would come home really fast.”

The Year 9 student’s Olympic dreams remain on hold, but the 15-years 100m breaststroke record is now Sienna’s to own.

She had come tantalisingly close at the Australian age championships in April, with a then personal best (PB) time of 1.07.72.

With the swim on Tuesday, she took 0.71 seconds off her PB and 0.48 seconds off Jones’ age record.

“Her former coach Michael Raubaum always told her, ‘you are only small, but you are six foot in the water’,” Mr Toohey said.

Along with Sienna’s mum Simone, Albury swim coach Wayne Gould and ACT Performance Centre head coach Shannon Rollason were poolside for the race.

Mr Toohey praised Year 10 Albury High student and swimming mate Isabelle Rae, who also swam strongly at the trials.

Competition at the elite national level gives the Albury girls the chance to truly test themselves against the very best swimmers, and the 200-metre breaststroke awaits them on Friday.

Sienna trains eight times a week in the pool, with additional strength sessions.

Mr Toohey said she had great support from the school.

“Her teachers do a really great job keeping her on track and making sure she gets her assignments done,” he said.

“She gets a lot of support, and they work hard to make sure she is up to date.

“Her maths teacher Georgia Jones was also an amazing swimmer at 15 years and understands what it takes.”