Muddy shoes and grubby school uniforms were once part and parcel of life for the average Australian primary school student, but it's becoming increasingly rare in the age of screens and organised indoor play.

But once a week students at a primary school in Australia's southernmost capital, students are making their own fun in a dedicated mud play pit, where splashing, flinging and squelching are commonplace.

Lansdowne Crescent Primary School in Hobart's inner south offers a weekly mud play day where children are encouraged to get outdoors and back into nature.

Kindergarten teacher Leearna Downham said the class was about getting back-to-basics.

Kindergarten teacher Leearna Downham says playing in the mud is "intrinsic for children". ( ABC News: Jessica Hayes )

"Playing in the mud or playing in dirt is natural, it's intrinsic for our children," she said.

"It allows them to be creative, it's open ended and it's always about the process not the product."

She said outdoor play days were about more than just getting dirty, they also encourage creativity and self-led learning.

"It's about developing a sense of self, a care for our world, each other, and getting back to nature," she said.

"It's really important in this day and age to get our children outside and exploring.

"It's not just playing, it's risk taking, it's problem solving, it's hypothesising and if you stand back and … observe, you can see so much learning going on.

"But it's not only what we're learning, it's also about how we're learning at the same time."

Mudplay is a "treasured time" for children at this Tasmanian primary school. ( ABC News: Jessica Hayes )

The program has been embraced by students and parents alike.

"They [the students] love this time, it's a treasured time, for the children, for us as teachers, and also our community," she said.

"They know that Wednesdays are their free-clothes day where they can get muddy and explore the outdoors."

Lansdowne Primary is one of a growing number of Tasmanian schools embracing nature play.

Jenny Dudgeon from the Tasmania Nature Play Network says "nature deficit disorder" is detrimental for children. ( ABC News: Jessica Hayes )

Jenny Dudgeon from the Tasmania Nature Play Network said unstructured outdoor play during school hours was becoming increasingly important, as students spend more time in front of computers and less time climbing trees.

"It's what I did when I was a kid, I think we've got a lot of teachers saying it's what they did as a child," she said.

"There has been that cotton wool parenting notion and nature deficit disorder, so kids are just not going outside.

Outdoor play needs to be extended to upper primary and secondary students, education experts say. ( ABC News: Jessica Hayes )

"We're noticing a lot of children don't have a lot of fine motor control and particularly gross motor control.

"There are also issues with eye development and we've got vitamin D deficiency happening because kids aren't getting out.

"But there's a whole lot of health and physical issues that can be addressed quite easily by going outside and putting down the screen as well."

Education expert Janet Dyment said there was a growing volume of research supporting the benefits of outdoor play.

Janet Dyment wants outdoor play extended across all school age groups. ( ABC News: Jessica Hayes )

An associate professor at the University of Tasmania's Education Faculty, Dr Dyment said outdoor play was highlighting the strengths of students who may struggle in conventional classrooms.

"There are some young people who don't thrive in the indoor-focused, NAPLAN-focused learning environments," she said.

"What happens when you take these young people outside is they become curious, inquiring young people that thrive and they become the most focused students in the outdoor setting."

The focus on the benefits of outdoor play declines after early childhood. ( ABC News: Jessica Hayes )

She believes outdoor play should be extended across Australian curriculums to middle and high school age groups.

"There are opportunities in the early years learning framework to allow that through their curriculum, but once you get into main schooling it gets trickier," she said.

"There's a big focus on early years, there's some focus in primary, and once you get to middle, high school and college it almost doesn't exist unless you're in a specialist outdoor education course.

Outdoor play helps develop fine and gross motor skills. ( ABC News: Jessica Hayes )

"It really requires teachers to look at the curriculum in innovative and creative ways and align their curriculum in that way and let the outdoors be a site for teaching and learning.

"Obviously policies need to support teachers to take young people outside to have teaching and learning happening in these important spaces."