The WA Premier has asked parents to keep children home from school if possible, with the last day of the current term brought forward to April 3.
The measure is to allow teachers to work on preparing remote teaching resources for term two.
Students who must attend school, for example children whose parents must work or children who cannot be cared for safely, are encouraged to attend and will continued to be taught until April 6.
After that public schools will provide supervision only, not teaching, until the end of term on April 9.
"From now until next Friday, all children who attend public schools will continue to be taught," Mr McGowan said.
"Staff will continue to be on hand to ensure that this can occur.
"However, the State Government encourages families to keep their children at home if they can access the online or other resources for the education of their children to continue.
Mr McGowan moved to reassure parents, saying the education system would continue to support families.
"I want to reassure parents that our schools are well prepared to continue to provide education for their children," Mr McGowan said.
Term two to look 'different'
WA Education Minister Sue Ellery said next week, from Monday March 30 to Friday April 3, lessons would be offered at schools.
She said the following week, in the four days beginning April 6, schools would provide supervision only, not teaching.
Ms Ellery said this would give teachers flexibility and time to prepare for how classes could operate in term two.
"With significantly less students attending next week, schools will have the flexibility to rearrange classes as appropriate," Ms Ellery said.
"This will reduce some of the pressure.
"In the week of the 6th of April, teachers and education assistants and other school staff begin the preparation for what education in a combination of physical school settings and distance and online education will look like in term two."
When asked whether earlier medical advice around the safety of sending children to school had changed, Ms Ellery said it had not.
"[This is about] ensuring that those people who need to stay working in the current circumstances can," she said.
"It is about recognising our staff need time to develop and prepare and do the professional development for what in term two is going to be a very different way of delivering.
"And it's recognising significant numbers of parents are already keeping their children at home."
Ms Ellery said term two would "look different".
"I think it will be a combination of physical attendance at schools, maybe some schools, maybe all schools, plus a combination of distanced education which will be hard copy packs and online," Ms Ellery said.
Independent and Catholic schools would introduce their own suitable arrangements, a statement from the WA Government said.
Late on Thursday, Catholic Education Western Australia confirmed it was following the Government's advice by asking parents to keep their children at home by close of school tomorrow if at all possible.
It said schools would be officially concluding the term on April 3, with the exception of seven schools in the Kimberley which were all closing tomorrow.
Ms Ellery said child care centres and after school care would continue in line with decisions made by the National Cabinet.
A Perth primary student had tested positive for COVID-19 overnight, but they been in isolation for 14 days and had no contact with their school, students or teachers, Ms Ellery said.
Queensland and South Australia have both announced they will go "student free" in coming weeks, although the schools will remain open for the children of parents working in essential services.
Plan 'extremely difficult to implement': Teachers' union
The State School Teachers' Union of WA (SSTUWA) has expressed frustration at the plan, saying the measures were unworkable.
"We understand the Government is facing unprecedented challenges at the moment, but these measures will be extremely difficult to implement," SSTUWA president Pat Byrne said.
"It is not possible for schools to make plans to accommodate students when they have no idea how many are actually going to turn up.
"They will not know how many classrooms they'll need or what lesson plans will be required until they arrive at school each day."
Ms Byrne also said teachers were still facing a lack of clarity around physical distancing measures.
"What schools need is certainty," Ms Byrne said.
"That's why we're calling on the Government to follow Victoria and Queensland and implement pupil free days across the system from Monday March 30, with the exception of at-risk students and the children of essential workers."