The Victorian Education Department has confirmed that last July it told state schools that 18-year-old asylum seeker students should no longer be enrolled on instructions from the Department of Immigration - which applied to those already 18 and meant the students could not complete the year.

But in November, the newly elected Coalition government reversed the policy, allowing teenage asylum seekers to complete their schooling after they turned 18, an Education Department spokesman said.

This came too late for some students, who had already left before they could finish high school.

Noble Park English Language School principal Enza Calabro said a small number of students had to leave her school after July. ''These students became very anxious and this created a sense of hopelessness amongst them,'' she said.

They were entitled to an additional 10 weeks through Adult Migrant Education Services.

Centre for Multicultural Youth chief executive Carmel Guerra said she also knew of students who had been removed from schools after July and found it ''appalling''.

She said some principals were advised they were unable to keep 18-year-old asylum seeker students, despite wanting them to stay on. Ms Guerra said that such children had lost ''a space in which they feel safe and secure in a new country, while their status is being determined''.

Dandenong High School now has 12 students who are in community detention. Principal Susan Ogden said last year teachers had been concerned for seven students who were set to lose their entitlement to a high school place after they turned 18. These students are now allowed to complete school following the changes.

One of those students, who turns 18 this year, feared he would have to leave school during year 11 until the policy changed. He said he was delighted when he found out he could finish school. ''It made me want to do something for Australia,'' he said.

A spokesman for the Education Department said it was unaware of how many students had returned to school after the Immigration Department's policy changed.

A spokeswoman for Immigration Minister Scott Morrison said: ''Eligibility for access to public schools is set by state and territory governments.''

She confirmed the Department of Immigration reviewed its schooling policy in the second half of 2013, which she said was finalised at the end of the year to make the existing policy more flexible.