Chace Harrison, Jalailah Jayne-Maree Jones, Zane Mellor, Addison Stewart, Jye Sheehan and Peter Dodt died after the incident at Hillcrest Primary School in Devonport in 2021.
They were enjoying end-of-year celebrations on the school's oval when a wind gust lifted the castle into the air.
Three other children were seriously injured in the accident, which made global headlines.
Rosemary Gamble, owner of Taz-Zorb which set up the equipment, pleaded not guilty to failing to comply with a workplace health and safety duty.
Magistrate Robert Webster is expected to deliver his decision on Friday morning in Devonport Magistrates Court, following a 10-day hearing in November.
Families of the children who died, including Zane Mellor's mother Georgie Burt, have been present during the court proceedings.
The court has been shown photos of the castle after the incident, as well as images of the pegs used.
It has been alleged pegs not compliant with national standards were used at only four of the castle's eight anchor points despite the manufacturer's instructions recommending eight.
In closing submissions in February, Gamble's lawyer Chris Dockray said Gamble had been left out to dry by the castle's Chinese manufacturer.
East Inflatables didn't provide instructions to Gamble upon purchase and only supplied four pegs, Mr Dockray told the court.
Gamble instead downloaded a two-page manual from the company's website, he said, which resulted in an interpretation that four pegs were sufficient.
The work, health and safety offence carries maximum fines of $1.5 million for a company and $300,000 for an individual acting as a business.
According to court documents, seven students were on the castle when a significant weather event dislodged it.
They fell from the castle, while a blower attached to the castle to keep it inflated struck a nearby student.
Preparations for an inquest have been paused due to the criminal proceedings, while a class action has also been launched against Gamble and the state of Tasmania.
A ceremony was held in Devonport in 2022 to mark the one-year anniversary, while there are plans for a permanent site to remember the children lost.
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