South Australian schools and pre-schools will be pupil-free in the week before the Easter holidays, with the State Government announcing a move to online learning in term two.

Key points: Schools will remain open next term for parents who do not have the capacity to keep students at home

Schools will remain open next term for parents who do not have the capacity to keep students at home The Government said some teachers would be working from home

The Government said some teachers would be working from home It said it was important to keep schools open, especially for vulnerable children

The SA Government said four pupil-free days before Good Friday would give teachers time to prepare to transition to "flexible learning" at the start of term two.

However, the teachers' union has slammed the announcement as "too little, too late", saying some staff were feeling "terrified" because of the risk to their health.

Education Minister John Gardner said schools would remain open in a "modified environment" for the children of parents who have to work, and for vulnerable children.

The measures are expected to apply across the Catholic and independent school sectors.

An Unley High School student with a measuring tape for social distancing. ( ABC News: Lincoln Rothall )

Mr Gardner said absenteeism across the board had reached 25 per cent and attempts were being made to move towards a remote learning model.

However schools will remain open for those families who need, as well as vulnerable students.

"It's very, very challenging to deliver an effective model of education when you're deal with two cohorts in an in-classroom environment and a learning-from-home environment," Mr Gardner said.

"We are giving these four pupil-free days to ensure that our teachers and our schools can become familiar with the resources we are providing for them.

"The message for parents is this — if you are capable of supervising your child at home so they can learn from home, we are now supporting you to do so.

"Some of those students are going to be learning from home, some of them are going to be learning at school, supervised, but some of the teachers will be doing the instruction working from home. Some of them will be in the school site.

"The model of learning must be consistent across those cohorts."

AEU SA president Lara Golding has called for the closure of schools. ( ABC News )

On Monday, SA Premier Steven Marshall defended the decision to keep schools open despite widespread confusion among parents about the preferred course of action.

The Australian Education Union's SA branch president Lara Golding said pupil-free days should be introduced immediately, rather than after another six school days.

"Parents are voting with their feet, and our members are rightly anxious and concerned about their own health and safety. Student-free days in week 11 is too little too late," Ms Golding said.

"Teachers are highly anxious — in fact, some are feeling quite terrified. There're so many confusing messages put forward by the Prime Minister and our Minister and Premier.

"There is no way that they can ensure social distancing in classrooms."

Some schools have 'majority' of students absent

The announcement follows similar moves by other states including Victoria, Tasmania and Queensland.

Queensland schools will become "student free" from next week, but will remain open for the children of essential workers.

Victorian schools began their holidays early, while parents in NSW have been told to keep children at home if they can.

In the ACT, many children are currently at home, with exceptions for families where parents are essential workers.

Yesterday, South Australia's Department for Education launched the Our Learning SA website for "families who are currently choosing to educate their children at home due to the current COVID-19 crisis".

Mr Gardner said daily absenteeism pre-coronavirus was typically around 10 per cent, but that had more than doubled in the past two weeks.

"Some schools … are operating in an almost business-as-usual environment in some communities, and some schools [have] very substantial absenteeism — the majority of their students absent," he said.

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Independent and Catholic school authorities have expressed support for the new arrangements, and will follow public schools in extending school holidays.

"Each school will look at its own particular circumstances but I believe many of them will choose to use those four days to prepare," said Carolyn Grantskalns, chief executive of the Association of Independent Schools of SA.

The union has expressed support for online learning, saying it was "keen to talk with the Government about what that would look like".

Unley High School closed after a student and a teacher contracted coronavirus. ( ABC News: Lincoln Rothall )

Until now, authorities have insisted on the need to keep students at school to prevent the spread of coronavirus.

Mr Gardner said, despite the apparent change, that remained the case, and that the "unambiguous advice" was for "schools and preschools to remain open".

Some schools in South Australia have already been forced to temporarily close because of coronavirus cases.

On Tuesday, Unley High School announced it was moving learning online for the remainder of the term after a teacher contracted COVID-19.