Families of the children killed and injured in Tasmania's 2021 jumping castle tragedy have launched a class action against the state and equipment operator.

Law firm Maurice Blackburn announced the move on Monday morning on behalf of lead plaintiffs Georgina Burt and Andrew Dodt, whose sons Zane and Peter died in the incident at Hillcrest Primary School in Devonport.

It was exactly three years after a jumping castle and zorb balls were lifted into the air by a wind gust during end-of-year celebrations at the school, killing six children and injuring three others.

In a writ lodged with the Supreme Court, the case alleged the state, as operators of the school, and the company that set up the equipment involved in the tragedy, Taz-Zorb, owed a duty of care for the students.

The case also alleged the defendants failed to take reasonable precautions to ensure the safety of the children taking part in the activities.

Principal lawyer at Maurice Blackburn Dimi Ioannou said the aim of the class action was "some accountability for what happened on that day".

"The families affected by the tragedy of what happened at Hillcrest feel the pain and the trauma of their loss every day," he said.

"Nothing will erase the suffering or bring back their lost children.

"This class action is the first step in the path to securing a measure of justice for the families affected by the Hillcrest tragedy."

Those eligible to join the class action included children who suffered a physical or psychological injury, witnesses and close family members of those killed or injured.

Rosemary Gamble, operator of Taz-Zorb has previously been accused of failing to comply with a health and safety duty.

Gamble, who pleaded not guilty to failing to comply with health and safety duties, was accused of only using pegs in four of eight anchorage points and failing to properly secure the castle.

It has also been alleged Gamble didn't follow the manufacturer's instructions and failed to properly train Taz-Zorb staff and take all reasonable steps to ensure children weren't exposed to risk.

A decision in that case was expected in February.

Chace Harrison, Jalailah Jayne-Maree Jones, Zane Mellor, Addison Stewart, Jye Sheehan and Peter Dodt died in the incident which was part of end-of-year celebrations on the school's oval on December 16, 2021.