The department of basic education is "extremely concerned" that schools across the country may be disrupted by the national Cosatu strike on Wednesday - which is set to also hit a range of private-sector and government services.

"It's extremely concerning that schools face the real threat of disruption," said the department's national spokesperson Elijah Mhlanga.

The Congress of South African Trade Unions (Cosatu) labour federation is embarking on a strike that it hopes will bring all nine provinces to a standstill.

"We hope it will not be the case because teachers know the practical implications of halting teaching and learning," said Mhlanga.

He urged parents to take their children to school on Wednesday.

"We hope the situation will be resolved without negatively affecting  school activities. We urge those protesting to do so without disrupting schools," he added.

Cosatu spokesperson Sizwe Pamla said the central message of the strike was to highlight the fight against job losses in the public and private sectors.

Pamla said thousands of workers were expected to strike.

"Even if workers don't take part, any worker who decides not to go to work tomorrow is protected by the [strike] certificate issued by Nedlac [the National Economic Development and Labour Council]," said Pamla.  

Nedlac issues certificates enabling unions to go on strikes.  

The SA Democratic Teachers' Union (Sadtu) said its members were joining the strike to voice their concern about the safety of teachers and pupils at schools being targeted by criminals.

"We will use the march to call for increased safety measures in our schools and to urge communities as well as the government to protect them," the union said.

Several other unions have voiced support for the strike, including the National Education Health and Allied Workers' Union (Nehawu), Police and Prisons Civil Rights Union (Popcru), National Union of Mineworkers (NUM) and the SA Commercial Catering and Allied Workers' Union (Saccawu).

Nehawu said its members were "greatly affected" by job losses, adding that Netcare and Mediclinic were in the process of retrenching close to 500 workers. Spokesperson Khaya Xaba said workers would join the strike but essential workers such as doctors and nurses would remain at work.

NUM said that in the mining sector alone around 40,000 people had been retrenched.

"Mines are closing operations daily. The government must immediately intervene in the mining sector to save workers from greedy mine owners who always leave workers high and dry after using them to up their dividends while working in horrible and unsafe conditions," said spokesperson Luphert Chilwane.

Cosatu's Pamla said they had called on the government and businesses during the job summit in 2018 to sign a moratorium freezing retrenchments.

The plan was for government and businesses to give proposals that emanated from the summit a chance.

"When we developed the framework after the summit, the private sector refused to sign the moratorium. Government did sign, but they have been failing to resolve the SABC issues, and now Eskom," said Pamla. "There is a huge possibility that workers can lose their jobs. It means government is also not prepared to honour that moratorium that they signed."

The march in Gauteng is expected to start at 9am on Wednesday at Mary Fitzgerald Square in Newtown and proceed to the provincial legislature. A memorandum of demands would be handed to premier David Makhura and business leaders.

Areas where marches will have an impact in the other provinces:

Limpopo: Marchers will gather at the SABC office park and go to the office of the premier, department of labour, Eskom and Anglo Platinum.

Mpumalanga: Lynnville stadium is the gathering point for a march to the department of labour.

Free state: In Welkom marchers will go to the offices of the department of mineral resources.

KwaZulu-Natal: A march will start at King DinuZulu Park. Memorandums will be handed to the premier, chamber of mines and department of labour.

North West: March starts at Montshiwa stadium and will proceed to the legislature.

Western Cape: March will proceed from Keizergracht Street in Cape Town to the Cape chamber of business, provincial government, city of Cape Town and parliament.

Northern Cape: In Kimberley marchers will start from the Kemo Hotel and march to the CCMA.

Eastern Cape: Marches are expected in the Nelson Mandela Metro, Queenstown, Mthatha and King Williams Town.