Students 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 December 2021.
Three other children were seriously injured in the accident, which made worldwide headlines.
They were enjoying end-of-year celebrations on the oval of the school in northwest Tasmania when a wind gust lifted the castle and several inflatable balls into the air.
Rosemary Gamble, the owner of Taz-Zorb, pleaded not guilty to failing to comply with health and safety duties.
She faced a 10-day hearing in Devonport Magistrates Court in November and Magistrate Robert Webster is expected to deliver his decision on Monday.
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.
One witness said the castle was tossed 75 metres by the mini-tornado, while one student recalled seeing her friend fall and another heard screams.
Engineering and weather experts, and the castle's Chinese manufacturers gave evidence at the hearing.
Gamble, who was charged in November 2023, is accused of failing to ensure the anchorage system was sufficient to prevent the castle from lifting.
It is alleged the castle was tethered at four of its eight anchorage points, not in line with the manufacturer's instructions, which required a peg at each point.
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.
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