The psych branch's foundation followed international trends in child welfare after the World War II. Educators were alert to the negative effects on children of social dislocation, migration, a changing employment environment, and the introduction of universal secondary education. Influenced by American developments, Jack Cannon, Victoria's assistant director of primary schools established the psych branch in 1947 and appointed a psychologist to run it. Only after the legal dispute with the Health Department affirmed the psych branch's scope, could its multidisciplinary team begin work. The idea was to maximise the potential of disadvantaged children, through a sophisticated case management model which embedded qualified social workers in schools. Being female, Joan Barrett and Elaine O'Neill walked a fine line in what was a male-dominated and hierarchical workplace. Their positions were classed as "temporary teacher" which secured a higher base salary and afforded school holidays off. For 20 years, Joan pioneered this professional role in student welfare at the psych branch, working full-time out of schools across Melbourne, doing cognitive assessments of children, working with their families to devise plans for their futures, making regular reports to austere superiors, and mentoring the next generation of social workers. Throughout this period, social work was developing a professional identity through the Australian Association of Social Workers, of which Joan was honorary secretary in 1950. In 1952, Joan married Paddy (Alfred George) Barrett, a tall, handsome and charming former commando and skilled rower. Two children, Claire and Joanna, followed. The couple separated around 1960. Joan's next job after the psych branch was as senior social worker in the Northern Territory. From 1969 to 1972, her base was Essington House, a youth assessment and training facility, and predecessor to Don Dale. Joan loved Darwin's colour, cultural diversity, and particularly working with Essington's clients. Most were young Aboriginal Australians with whom she developed an affinity. Some stayed in touch with Joan after she left the north.

Back in Melbourne in 1973, Joan continued to work with young people at the Department of Family Welfare's Baltara Reception Centre. Her clients were boys aged 10 to 15 who came into state care from police or court orders, often following foster-family breakdowns. Many were Australian Aboriginal children who had been removed from birth families. After her years at Essington House in Darwin, Joan was especially skilled and respectful in her work with these residents, overseeing all of the case work practice concerning them. Joan encouraged reunification of birth families wherever possible, going to great lengths to connect with potential community supports and youth workers. Ahead of her time, she was an early advocate for a dedicated Aboriginal placement body in Victoria, now the Victorian Aboriginal Child Agency. Colleagues report that Joan demonstrated compassion, empathy and patience in her casework. She finished her working life in part-time positions with community organisations at Hawthorn. Joan lived most of her life in Victoria, yet her heart was firmly planted in Western Australia. Her childhood home was Toompup, a railway siding 400 kilometres south-east of Perth, one of many localities in the region named in Noongar language and ending in the syllable "up", meaning "place". Joan was born in Albany, the second of three children to Phyllis Martha Fletcher and George Oliphant Duncan, a First World War veteran. George established a sheep and wheat farm at Toompup. In recognition of his Melbourne birthplace, he named the farm Boroondara. All her life, Joan practised environmentalism, aiming to leave as small a footprint as possible: gardening, composting, recycling, and avoiding waste. Every aspect of gardening was a studied exercise, necessitating consultation with experts, texts, and gardening groups. The importance of trees in the environment was emphasised during her years at Albany High School. Annual Arbour Day planting was begun at Albany High in 1925 by the inaugural Principal, Francis Reedy, formerly of Perth's Modern School. Reedy wanted children to be "tree-conscious", recognise their beautifying aspects and plant them to counter the destruction executed by early settlers. On Arbour Day in 1942, Joan and her fellow students added hundreds of saplings to the school's existing plantation of 16,000 trees. Later in life, with characteristic energy and commitment, Joan wholly embraced Australian native plants and garden design, through the Society for Growing Australian Plants. Systematically, she removed every exotic plant from her Kew garden. From the blank canvas, she artfully recreated nature in a series of garden "rooms" replete with gently winding paths, bushy shrubs, delicate flowers, and exquisite trees, including specimens from her home state of Western Australia. Each one was carefully selected for its beauteous trunk, bark, leaves or blossoms. While tending her garden, Joan had a steady companion in ABC local radio. Her listening was punctuated by lunch and reading every detail of The Age, with the Oxford Dictionary at hand, copies being at the front and rear of the house, should the need arise.

Joan's circle of friends remember her as a lively and live-minded individual. At the University of Western Australia, she made lifelong friendships. Living at Women's College during her studies in social work, she befriended undergraduates and graduate students alike. Some of the Women's College students called each other by variants of their surnames, a practice that stuck. In her university circle, Joan was forever known as "Dunc". As a teacher of social work students on placement, Joan was a generous supervisor and gentle mentor. To fellow staff, she was a warm and considered colleague whose outlook was positive. In retirement, she volunteered at Kew Community House where she made soup every week for lunch and delivered the Meals on Wheels solo. When visitors or family arrived at her Kew home, homemade delights appeared with a cup of tea. Later, as a resident in aged care, Joan demonstrated a genuine connectedness with those around her, encouraging everyone to participate in the dinner table conversation and listening to their stories. Joan Barrett was a self-effacing individual, with an uncommon humanity, a generosity of spirit, and an inherent love of the environment. Her sister, Peg, and daughters Claire and Joanna survive her. Madonna Grehan wrote this with help from family and friends.