Almost 6000 students from 175 schools took part last year and similar numbers were expected in Devonport and Hobart over four days in November.

Both venues stage primary and secondary events in which Grade 3-12 students complete a swim, ride and run individually, in teams or both.

Event director Tim Smith said the current limit of 500 on mass gatherings and social distancing rules of 1.5 metres meant that it was not possible to hold an event of this scale.

"Given the uncertainty that the event will even be allowed to proceed by November, it is just not worth building up expectation at this point with such a high likelihood that in the end we will not be able to hold the event anyway," he said.

"The event also brings together students from all over the state and if any active cases of COVID-19 were in the state at the time, it would make it extremely difficult to proceed safely."

Smith said considerable time goes into planning the event with schools organising entries, transport, volunteers and students.

Complying with COVID-19 restrictions at a public venue with multiple access points was considered unworkable.

"As the race organiser I am ultimately responsible for the safety and well-being of all participants, officials, volunteers and service providers. Given the large scale of the event and current restrictions, combined with the amount of time and commitment to stage the event and how students interact en masse, it was simply not possible to continue this year."