Parents, staff and alumni were told of Dr Horton's resignation on Monday, April 15.

Dr Horton became TAS principal in July, 2021. She replaced Murray Guest, who led the school for 21 years before he was killed in a car crash in October, 2019.

In a letter, TAS chairman Sebastian Hempel said the school had notched record enrolments under Dr Horton's leadership.

He acknowledged her "commitment, professionalism and perseverance".

"Rachel has overseen the ongoing successful implementation and growth of co-education across the school, further embedding the broad opportunities available to all TAS students," Mr Hempel said.

"[Dr Horton] has been a fantastic role model for all students and has built a high level of engagement with, and respect from, the broader TAS community."

Dr Horton said she was sad to be leaving, however, it was the right time for her to "move on and seek new challenges".

"I will continue to work hard for the school over the next six months and will then be taking some time off with my husband before we turn our thoughts to new opportunities," she said.

Under Dr Horton's leadership, TAS has continued to grow, enrolling 682 students, including 238 boarders.

Dr Horton oversaw the construction of a new, 64-bed boarding house, expected to be completed by the end of the year.

Born and raised on a farm in England, Dr Horton has notched notable career milestones.

She holds a PhD in Immunology, did a tour of duty in Iraq in the British Army and is an international rugby referee.

Before taking on the role as principal at TAS, Dr Horton was deputy headmaster at Brighton Grammar School in Victoria and before that, taught chemistry and physics at Churchie in Brisbane.

But in recent times, Dr Horton's passion for rugby union saw her touring the world.

A former player, Dr Horton became an international referee in the sport.

In February, she was appointed television match official at the Women's Six Nations, a tournament between England, France, Ireland, Italy, Scotland and Wales.

Dr Horton is currently overseas and has just ruled on the April 20 fixture between England and Ireland at Twickenham.

She is scheduled to head to Cardiff for the match between Wales and Italy at Principality Stadium.

Following the Six Nations, Dr Horton will travel to New Zealand for the Pacific Fours which is contested between Australia, Canada, New Zealand and the United States.

In her LinkedIn page, Dr Horton said,"I continue to referee and also referee coach, hoping to grow the game and mentor the next generation."

TAS deputy principal Ray Pearson will take on the role of acting principal from October 1 until a new principal is appointed.