Schools in Barnet and Potters Bar are gearing up for Wednesday’s planned national teachers' strike.
Barnet Council and Hertfordshire County Council are compiling lists of the schools that will be closed or affected by the National Union of Teachers walk-out.
The NUT has organised the industrial action following a row with the Government over planned changes to pay, pensions and working conditions.
Local authorities have urged schools to contact parents as soon as they know the extent of the impact the strike will have.
Barnet Council said today it would be publishing a list of affected schools as soon as it is finalised.
Chris Hayward, cabinet member for enterprise, education and skills at Hertfordshire County Council, said: "While we recognise that there are strongly held feelings on both sides of this national dispute, strike action in a key public service like this can only be to the detriment of Hertfordshire’s children and their parents.
“We hope there is a speedy resolution to this dispute in the interests of all concerned. The decision to stay open or to close is for individual school headteachers and governors to make.
“We have urged as many schools as possible to remain open as long as it is safe to do so, but we do not have any authority to compel them to stay open, whether they are community schools, free schools or academies.”