Perth schools will flush their drinking water pipes at the beginning of every school year over lead contamination concerns.

Last year the state's chemical testing centre chief executive warned schools were at risk of contamination, and recommended pipes be flushed, after problems with the pipes at the $1.2 billion new Perth Children's Hospital emerged.

WA Education Minister Sue Ellery said existing schools had begun flushing their pipes ahead of classes resuming on January 31.

Ms Ellery said there were no concerns about contamination in pipes but the flushing was an "added safety measure".

"This is a new protocol that we have put in place to start for this year — every year at the start of the year we'll do a flush just to make sure there's no stagnant water in the system," Ms Ellery said.

Ms Ellery said the new regime was not required by the health authorities but would give parents an "added measure of confidence".

In addition, from this year, new schools will have their water tested for lead levels.

The new Perth Children's Hospital remains closed after it emerged in 2016 there were high levels of lead in its water.

New schools for Perth's outer sprawl

The State Government today also announced construction will begin this year on three new primary schools in Perth's outer-suburbs, to cater for the growing population.

The Government will spend more than $55 million to build the facilities in Baldivis, Banksia Grove and Caversham, as part of an election commitment made last year.

The aim is for them to be open in 2020.

The Baldivis school, in Perth's south, will have places for 430 students and include music and arts facilities at a cost of $16 million.

According to the latest census data, Baldivis has a higher-than-average proportion of young children, with children aged 0-4 making up 10.4 per cent of the population compared to 6.5 per cent across the state.

The number of children in government primary schools is also higher than the state average — 25.8 per cent compared with 18.9 per cent state-wide.

The WA Government said the population of the area had increased rapidly in the past five years, by more than 3,100 people on average every year.

Banksia Grove east primary school, in Perth's north, will cater to 540 students at a cost of $22 million.

At the time of the election promise, Labor said it would also build new schools in Burns Beach and Yanchep to better cater for population growth in the northern suburbs.

Caversham South primary school, in the north-east of the city, will have a capacity for 430 students and cost $17.3 million.

The former WA Liberal government scrapped plans for a new school in the district in 2015.

Strike action looms despite backflip on education cuts

The announcements come as industrial action looms over state schools, with administration and support staff threatening to strike in the first week of school, next week.

In mid-December, the WA Government announced $64 million in cuts to the education budget over four years.

But earlier this month it said it would reverse $23 million worth of these measures, including its decision to close five schools, axe the School of the Air, and the Gifted and Talented program, and close accommodation at Northam Residential College, following a strong public backlash.

Community and Public Sector Union WA branch assistant secretary Rikki Hendon said up to 200 education and support staff would walk off the job at lunch time on Thursday over cuts to jobs.

"We'll be undertaking industrial action with our staff in the Department of Education, particularly those in central and regional offices, they'll be coming out, they'll be coming to rally and it will be very likely they won't be coming back to work that day," Ms Hendon said.

She said it would be the start of a wave of planned industrial action that would be rolled out unless the Government backed down.

Premier Mark McGowan said he was not concerned the industrial action would mar the start of the school year but urged the union to "pull back".

"What we've done is a voluntary, targeted redundancy scheme so it's voluntary for the people who work in the public sector and I think public servants generally like that," Mr McGowan said.

"I'd ask the union to understand that public servants want this approach, it gives them choice and it also saves the taxpayers money."