The Andrews Government has broken a pre-election promise by removing religious instruction from state school classrooms, the Victorian Opposition says.

As of next year, state school students will not be able to study specialist religious instruction (SRI) during class time and will instead have do the study before or after school or during lunchtime.

Opposition education spokesman Nick Wakeling said it was not what Premier Daniel Andrews promised.

"The Government promised Victorian families prior to the last election that the current arrangements would continue under their Government," he said.

"This is clearly not going to happen as part of this announcement.

"We call on the Premier to reverse this decision and to deliver on what he promised Victorian families."

Only about 20 per cent of students participate in religious education on an opt-in basis.

Education Minister James Merlino said under the current rules, the remaining 80 per cent of students were not allowed to undertake any curriculum work during that 30-minute period.

"In the education state, that's just not the right thing to do," Mr Merlino said.

Mr Merlino said he understood that some parents would be angry about the decision, but it was the "right thing to do".

"Curriculum time is precious for our kids," he said.

"We want every second, every minute of curriculum time being devoted to teaching and learning provided by qualified teachers."

The way religion is taught in Victorian primary schools was overhauled after a report found that Education Department guidelines were being breached by the key provider of SRI, Access Ministries.

Victoria also banned religious organisations from running prayer groups, handing out Bibles and delivering other unauthorised information sessions in state schools during school hours.

Wishes of parents 'disrespected'

Rob Ward, from ACCESS Ministries, expressed disappointment at the lack of consultation around the decision.

He said many Australians generally agreed that Christianity had been "a benefit to society" and the Government has taken away an opportunity for students to learn more about all faiths.

"I think they're disrespecting the wishes of parents by not chatting to anybody about it but by simply making an announcement," he said.

"I think there's such a demand for SRI [that] we're certainly going to encourage the Government to rethink its decision.

"We think it's been rushed."