Significant concerns have been raised about Buchanan and St Ambrose High Schools in Coatbridge, North Lanarkshire, built on a former landfill site, after incidents of blue water coming from taps.
Members of the NASUWT union at Buchanan High are walking out on Thursday 20 to Friday 28 June.
NASUWT members at St Ambrose High will take strike action on 25, 26, 27 and 28 June.
The council has insisted the schools and the site are safe.
Buchanan High was closed to pupils on Thursday.
Gerard McLaughlin, head of education at North Lanarkshire Council, said: “Despite the facts being presented about the water being safe at the school campus and evidence demonstrating that it has been since early December and as recently as April 29, and that public health has stated there is no evidence to support a link between blue water at the school or the site itself and any serious ill health, the NASUWT has decided to take industrial action at Buchanan High School.
“This follows extensive dialogue between senior council officials and representatives of the NASUWT over the last 24 hours.
“We understand the impact that this will have on pupils and parents at Buchanan High School as a direct consequence of this action.
“Having assessed the potential impact, we have regrettably decided that Buchanan High School will be unable to receive pupils during the period of industrial action due to the specific medical needs of some of the pupils.
“Neither the school nor the council would ever take any risks with young people’s safety.
“Despite our disappointment that the NASUWT has taken this decision, we will remain in dialogue with trade union officials over the coming days.”
The Scottish Government last week set up an independent review to help address the fears of parents and teachers.
Paul Cackette and Dr Margaret Hannah, who are leading the review, met the headteachers of both schools, as well as public health experts and other representatives from North Lanarkshire Council on Wednesday.
They are making arrangements to meet parents next week.
The review is tasked with looking at specific health and safety concerns raised at the shared site, as well as the history, construction and maintenance of the campus.
It will examine health concerns, including possible exposure to unspecified chemicals in the water resulting from previous land use at the new school site, to see if these are linked to developing cancer.
The probe is set to be completed “as soon as practicable” and ahead of the next school year.
NASUWT general secretary Chris Keates said: “Our members are suffering deep stress and anxiety about their health and welfare due to the failure of their employer to take the necessary action to provide assurances about the safety of the site.
“While the independent review promised by the Scottish Government is a welcome development it still does not commit to a full comprehensive site survey which tests the water, air, soil and fabric of the building.
“Teachers are deeply anxious about whether there is any link between conditions at the School, including the blue water and a range of health issues among staff.
“The site survey should be commissioned immediately and as the end of term is only a matter of days away, the schools closed to enable the work to begin and at least give teachers and indeed pupils and parents some respite from the daily anxiety of having to attend the school site. As the local authority has refused to act to protect teachers the NASUWT will.”
Jane Peckham, NASUWT national official for Scotland, added: “We thank those parents and other members of the school community who have shown support for the strike and who stand with the NASUWT in calling for immediate and robust action to address these issues and to make sure the health of staff and pupils at the campus is safeguarded and prioritised.”
More than 16,000 people have signed a petition calling for an investigation and for staff and pupils to be tested for toxins.
The site was used as landfill from 1945 to 1972 and domestic refuse and waste materials from the former Gartsherrie Steelworks were deposited there.
Tests at the campus found higher levels of copper in the water in some areas of the school, which can lead to discolouration.
More than 1,800 metres of copper piping has been replaced with plastic pipes across the site, opened in 2012, which also includes Townhead Community Centre.