There has been a 60 per cent increase in international students enrolled at Victorian state schools over the past four years.

Some sought-after schools with large international student cohorts have knocked back the siblings of existing students if they live just outside the enrolment zone.

Cate Hall, a spokeswoman for public school lobby group Our Children Our Schools, said she was concerned overseas students were displacing local students at full schools.

"While there are no doubt two-way cultural and financial benefits from having international students in our schools, the sharp increase in numbers needs to be looked at further in light of the capacity issues in many of our public schools," she said.

There are currently 4352 international students studying at Victorian state schools, with the majority of these students coming from China, Vietnam, Saudi Arabia, India and Korea.

East Doncaster Secondary College has the most international students, with 118 enrolments, while Balwyn High, Northcote High School, Kew High School, Strathmore Secondary College, Camberwell High School, Brighton Secondary College and Elwood College all have between 70 and 94 overseas students. Many of these schools have strict enrolment zones because they are so popular.

One parent, who did not want to be named, said her first child had been accepted into a school just outside their zone but her second child had not.

The sought-after inner-city school has more than 70 international students.

"It doesn't make sense to me. You would have thought that siblings would have been prioritised," she said.

Parents Victoria executive officer Gail McHardy said many schools enrolled international students for the extra funds.

"If there is limited space and an international student takes it, they could be taking the spot of a local residing student," she said.

Schools receive around $15,000 per international student enrolment, and the Education Department said this paid for the cost of their education and welfare, language and support services.

Another Melbourne parent questioned the fairness of the situation.

"If a school can accommodate more children than those who live in its zone, shouldn't those places be going to kids who are Australian residents? I ask this not on xenophobic grounds but on fairness grounds."

An Education Department spokesman said international students cannot take the place of a local student at their local school.

"The number one priority for Victorian schools is and must be to enrol students residing within their designated neighbourhood boundary," a department spokesman said.

The spokesman's views were echoed by Victorian Association of State Secondary Principals president Judy Crowe, who said international students usually enrolled at Victorian schools during the final years of schooling, when there was less demand.

She said they filled VCE classes, making them more viable.

"At VCE you would have some classes that wouldn't have the maximum number of students enrolled in them. They are typically the subjects international students want to do like physics, chemistry and maths and the business subjects," she said.

But she said the biggest benefit of international students was that they "broadened the horizons of local students".

She said they were not the "cash cows" that they were perceived to be.

Recent changes to student visa rules are expected to increase the number of international students in primary schools. For the first time, Chinese children will be able to make visa applications for primary school admission.