Dissatisfied families are redefining education in Victoria, with almost one in two students changing primary or secondary schools at least once.

A staggering 40,000 Victorian students moved in and out of government, Catholic and independent schools in 2015.

Bullying, aspirations and toxic friendships are behind the churn, according to academics.

And some students have no choice, and change schools because they move house, are expelled or shuffled between foster homes.

The Victorian Curriculum and Assessment Authority estimates that between 4 to 5 per cent of students changed schools last year. This excludes students moving from primary to secondary school.

A Fairfax Media analysis found that if this trend continues, and you assume any student has the same chance of switching schools once any given year, a child starting prep last year has between a 41 per cent and 49 per cent chance of changing schools at least once by the time they finish year 12.

There are higher rates of student mobility during the start and end of high school, with 5 per cent of all students moving in years 7, 10 and 11.

Finding the perfect school was a case of third time lucky for Marine Chu.

Marine Chu has spoken to many students who have moved schools for various reasons. Photo: Eddie Jim

The Mac.Robertson Girls High School student, started at Dandenong High School in year 7, and then enrolled at St Albans Secondary College when she moved house.

The 18-year-old said she decided to move again in year 9 because she did not feel challenged enough. "I was doing well at St Albans but when I came to Mac.Rob I became average. I liked being average for once," she said.

"I'm with friends who have the same ambitions. It's nice to feel like you are part of a big group of people who value the same things."

Ms Chu, who is a former executive member of the Victoria Student Representative Council, has spoken to many students who have moved schools because they are bullied or have experienced mental health issues and want a fresh start.

Joel Windle, a senior research fellow at Monash University said many families move schools for strategic reasons.

His research has identified a pattern where students attend state schools for the first few years of high school [and hire tutors], and then apply for select-entry schools or scholarships at private schools.

"They try to move up in the food chain, or the school market," Dr Windle said.

"It's easier for parents who have a child with good grades or what they call 'selling points' which is academic or musical talents."

He said that this phenomenon had a negative impact on mainstream state schools, who lost many of their top students and were left with students with higher needs.

Changing schools can come at a cost.

Recent research by the NSW Education Department found that students who changed schools several times performed worse in NAPLAN than their classmates and were more likely to drop out.

It mirrored international research and found "mobility has a detrimental impact on student outcomes".

RMIT and Deakin professor Helen McGrath, who is a member of the National Centre Against Bullying and runs a counselling practice, said families should think carefully about changing schools.

They should first try to address issues with their existing school, and if it cannot be resolved, consider moving. The main issues she encounters at her practice are bullying and friendship breakdowns, particularly among girls.

"Sometimes it is not salvageable, sometimes the child has had enough," she said.

"It's a big step to change schools. It creates a period of time when you can't focus on learning but you are focused on settling in socially and trying to work out where the rooms are. Parents need to know that."

Victoria University's Professor Kitty te Riele said high student mobility was linked to disadvantage. "They might be in residential care, or their family might be living in poverty and if a job opportunity comes up, they will move," she said.

She said that uniform and textbook costs, making new friends and catching up on school work were challenges for these students.

An Education Department spokesman said transition officers worked with schools to help them support students changing schools.