Thousands of students have been denied their hopes of attending the Schoolies Festival in Victor Harbor.
Police Commissioner Grant Stevens confirmed the 2020 event has been cancelled because of risks associated with COVID-19.
Speaking alongside Premier Steven Marshall during a coronavirus update on Friday, Mr Stevens said final advice in regards to the festival was being prepared.
"The major Schoolies event will not be occurring and there will be no major gathering in the Fleurieu Peninsula area," he said.
"We will consider restrictions being placed on short-term accommodation, which includes caravan parks, Air BNBs and other rental properties, to ensure that we don't have mass surges of people into private venues.
"We will also be making sure that we have a mechanism in place to provide a safe environment for young people who choose to visit holiday destinations in South Australia that weekend, so they can enjoy their end-of-year celebrations, but also have some assurances that they can do so safely."
Regarding caps on accommodation, Mr Stevens said plans were still being finished, but there had been discussions about limiting the number of beds within rental accommodation.
"The total number of people within a rental accommodation should not exceed the total number of beds and there is already a cap of 50 people at private dwellings which will not change," Mr Stevens said.
"Caravan parks and accommodation sites will have a cap which is yet to be decided in terms of the total number of people that can be on one site."
Mr Stevens said police would have "dedicated resources in place to ensure compliance".
"Given the nature of the traditional Schoolies event and the desire to ensure people participate safely, we will have additional resources in those key areas... to make sure that anyone in those locations has access to medical assistance, ambulance, police and other support mechanisms," he said.
"There is no capacity to properly manage large crowds in a COVID-safe way.
"In the absence of any ability to do so, the logical decision is to not let those events occur."
More than 3000 bookings have already been made at caravan parks and holiday homes across the Fleurieu Peninsula and school leavers are still expected to travel to Victor Harbor at the festival weekend.
Encounter Youth CEO Nigel Knowles said all 2020 Schoolies Festival ticket holders would be directly contacted and issued with a refund within 14 days.
"Following the decision made today, 18 September 2020, we still want to encourage young people to celebrate safely. For 21 years, we have supported young people in celebrating the conclusion of Year 12," Mr Knowles said.
"2020 will be no different. We will still be present in support of our Year 12s.
"From here, we encourage all Year 12s organising an alternate end-of-year celebration, those who attend a celebration or parents who want to support them, to register their celebration by completing the survey we will send you.
"We will utilise this information to provide planning and support where possible to the Class of 2020.
"We thank you for your patience and understanding. Should you have questions about Schoolies Festival, we encourage you to contact us at firstname.lastname@example.org."
City of Victor Harbor Mayor Moira Jenkins said she understood the decision would come as a disappointment for school leavers.
"The Victor Harbor Schoolies Festival has been an annual rite of passage for South Australian teenagers for over 20 years. While the class of 2020 deserve recognition for their hard work, this year is like no other and as a community we need to do everything we can to keep COVID safe. In this case, it means cancellation of the 2020 Schoolies Festival," Dr Jenkins said.
"We encourage private accommodation providers to be flexible in their cancellation and postponement policies to support the cancellation of the 2020 Schoolies Festival and help spread bookings more evenly over the coming months and summer holiday period.
"There is no doubt that tourism is an important part of Victor Harbor's economic recovery and we encourage families and small groups to visit and enjoy the wonderful experiences on offer in our region.
"Mass gatherings like Schoolies Festival are not the answer to our region's economic recovery. We want to see bookings spread out, with smaller groups out and about within our community. The Council has taken on this mindset and organised a smaller series of events between October and December to provide locals and visitors with activities and vibrancy.
"Local businesses and our wider community have done a fantastic job adapting to restrictions and government directives to keep our community and visitors COVID safe. It is important we do all that we can to maintain this position."