"I've missed you," Levi, 10, says.

He means those words and speaks them with ease as he finds the shelves of toys, games and books in the office.

Levi, who has Down syndrome, once could only be understood by his family. But starting with sounds then words, phrases and sentences, Ms Johnstone gradually helped him converse with new acquaintances and even order the occasional ice cream.

She also helped Naomi to process words and to strengthen her language after the 11-year-old missed blocks of school during four surgeries and treatment for a brain tumour. Naomi has been reading novels with Ms Johnstone's help.

"She has the best jokes," Naomi says.

Some of her young clients, who might begin with stutters or be non-verbal, play with cards or board games requiring language. Others shoot foam bullets from a toy gun at a target and notch up new words to say.

"We use games and fun to create opportunities for communication," Ms Johnstone says. "There's always fun at speech therapy."

There have been possibly 1000 clients who would agree Ms Johnstone's career has helped them. She had clients in nearly every school in south-west Victoria, mostly in Warrnambool.

Ms Johnstone is now retiring to spend more time with family after 40 years earlier taking her first job at South West Healthcare and beginning a private practice in the city.

"I was one of those lucky people who found what they wanted to do at age nine," she said.

"I have never grown tired of speech pathology because of the diversity of people I have worked with and it's been an absolute privilege to be part of people's lives when there are significant challenges."

Ms Johnstone is particularly moved by one client who she worked with after a bus accident and continues to meet with her more than a decade later.

"When you have a significant brain injury and you have no verbal skills after having had them; the loss is so significant," she said.

"When you can help recover speech for that person it becomes more important than their physical recovery because they recover their identity."

Anna Philpot, Levi and Naomi's mum, said Ms Johnstone had left a legacy in Warrnambool and helped her children face challenging goals.

"She is an amazing woman," Ms Philpot says. "There are big shoes to fill."

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