Tiny 100-year-olds filed through the gates of St Patrick's Primary School on Wednesday, replacing the usual boisterous five and six-year-olds that stream into the infant classrooms.

"Today we're celebrating them being 100 days smarter," teacher Eliza Tyndall said.

"Because we've had such unprecedented times we just thought they needed a bit of a celebration, especially with everything that's going on."

The celebration also builds on a classroom focus on figures, fellow teacher Louside Hill said.

"We've been doing fun things with the kids to do with numbers," teacher Louise Hill said.

"Counting to 100 by twos, fives, tens.

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"Asking them if they had $100 what would they spend it on, what they think they'll be doing when they're 100, colour by number to 100.

"They also made crowns and glasses, and we've got a party at 1 o'clock, which is also 100."

The big day was a great way to make special memories of regular milestones during a very strange time for the world, principal Michael Morrell said.

"They've missed so many milestones and celebrations that you get as a kindergarten student," he explained.

"It's just been wonderful to see our kindergarten teachers put so much time and effort into giving these kids this opportunity that's a special memory for them.

"It helps them understand number, so they actually count the days, they look at the number chart and it actually relates to their awareness of number.

"When they hit that 100 mark, it's a significant three-digit number and they usually celebrate with a party."