St Ambrose and Buchanan high schools moved to a purpose-built shared campus in Coatbridge in 2012. The site was previously used as a dumping ground for various industrial waste in the post-war era by local engineering firms.
Council officials insist the land was thoroughly cleared and made safe before the schools were built.
Now the Scottish Government has confirmed that testing will now be carried out at the campus, led by Scottish Water and the Scottish Environemental Protection Agency (SEPA).
The specific detail and locations of the testing will be determined by the review team in conjunction with SEPA and other environmental health bodies.
The work follows a recommendation by the independent review team appointed by John Swinney. The team will look at specific health and safety concerns as well as the history, construction and maintenance of the school campus.
The results of the tests will be published as part of the report due ahead of the school opening on 12 August.
The Scottish Conservatives’ education spokeswoman Liz Smith said: “It’s a relief to see that the SNP have finally agreed to carry out these tests.
“Requests for further testing had been raised weeks ago, but the Scottish Government have been slow to react.
“The trust between the local government and parents and teachers is clearly breaking down, and they need assurances.
“Hopefully these tests will provide the answers we need, but if not a full independent inquiry may be needed to help these schools come back together.”
Concerns were raised about the Coatbridge campus in March last year after blue water was found coming from pipes in the new buildings, with tests later revealing higher than recommended levels of copper. Officials said this was due to corrosion and insisted there was no health risk.
Fears among staff and pupils came to a head when it then emerged that four former or current members of staff at Buchanan High had received treatment for cancer. The local health board say specialist doctors have confirmed that no incidence of cancer - or any other serious illness - was caused by the schools or the site on which they were built.