Co-manager of bridal and formal wear shop Shazzam at Toronto Jenny Wilson said many girls had started shopping for their gowns earlier this year and she estimated about 50 per cent had already purchased their dresses.

"We have not had any noticeable decline in sales because it's [the moratorium] only just happened in the last few days, but we are anticipating we may," she said.

Ms Wilson said she believed students were still likely to dress up and gather - while abiding by government restrictions - either in small groups or online.

"Everyone I've spoken to, even mums, have said 'If the school is not putting a formal on they'll be having something either at our place, or as soon as there is allowed to be a crowd'," she said.

"A lot of the kids have said 'We'll dress up anyway and have photos done' and all that sort of thing. So I do think essentially it will still happen, it will just be different, like everything else in the world is at the moment.

"I definitely think there will be some worried mums nervous about buying gowns for their girls, but I think the kids will make it happen somehow.

"They want the pics in their glamorous gown, the hair and the makeup, all of that sort of thing, so even if it's done five at a time or something, or they Zoom it, or whatever they do, I feel they will make it happen in some way shape or form... I think eventually they will celebrate it somehow."

As previously reported, the state government introduced additional guidelines for schools last week, including students staying within their relevant cohort group.

"School formals, dances, graduation or other social events are not permitted," the guidelines said.

"Schools may hold a year 12 assembly at school without parents to recognise the completion of school. Schools may consider delaying events until later in the year."

More than 47,000 people have signed a change.org petition asking the government to consider alternatives to blanket cancellations, such as multiple staged graduation assemblies or formals.

The petition said corporate events can have 150 people or one person per four square metres, whichever is the lesser. Hospitality venues can have 300 or one person per four square metres.

Ms Wilson said postponing formals for a few months rather than cancelling them all together is "what we're hoping will happen".

She said formals were often the highlight of students' lives so far. "It's the coming of age," she said.

"It's when they first get the whole package - the hair, the makeup, the beautiful gown, all the lovely pics - it's a memory for the rest of their life, it's very special."

She said Shazzam was still hosting individual appointments for girls searching for their dream dresses.

She said floor-length gowns in gold and jewel hues such as royal blue, emerald green and ruby red were popular.

"There's lots of glitz and glamour, a lot of sparkle," she said.

"A lot of sequinned gowns, lurex style gowns, plunging necklines and high splits."

Jack Lebrocq, director of Hummer and limousine company Arrive First Class, said COVID-19 uncertainty had "massively" affected his business.

"In terms of formals, September is when we come into peak season and if formals are a no-go we will probably lose 30 per cent of our revenue for the year."

Mr Lebrocq said last year the company had bookings from Monday to Sunday and most of the midweek jobs were formals.

"Because we're such a big fleet - we have seven vehicles - some weeks we would have all seven vehicles on the road," he said.

"If you times that by what we charge, [the effect of COVID-19] is quite disappointing. But we can't do anything about it, it is what it is, we're not going to kick stones. There are a lot of other people in worse positions. I feel more sorry for the actual students."

Mr Lebrocq said many schools and students had spent months waiting to see how government restrictions would evolve.

"These formals are booked at venues, which can only take bookings up to a certain amount of people and it just won't be able to happen," he said.

"Normally by July and August we have a flood of inquiries, but we've probably only had a handful of inquiries.

"Only a week away from September and there are no formal bookings in. By now we would probably have 15 to 20 bookings by this stage and by September that's when it really starts to crank up."

He said the company was "absolutely ready to go" if and when the moratorium lifts.