The biggest strike in a decade is under way, with up to half a million workers walking out in increasingly bitter disputes over pay, jobs and conditions.
Members of seven trade unions are taking industrial action, affecting schools, universities, trains and buses.
Thousands of schools closed for the day because of action by the National Education Union (NEU), although many parents only found out on Wednesday morning if their children would have to stay at home.
Civil servants, train and bus drivers and university staff also stopped work on the biggest single day of strikes in a decade.
Picket lines were mounted outside railway stations, schools, government departments and universities across the country, with unions saying they are receiving strong support from the public.
More than 100,000 members of the Public and Commercial Services (PCS) union are on strike, including Border Agency staff at ports and airports.
The union announced on Tuesday night that its Border Force members in France will strike during the February half-term.
The TUC is holding a series of protests against the Government’s controversial plans for a new law on minimum levels of service during strikes.
A petition against the law, signed by more than 200,000 members of the public, will be handed in to 10 Downing Street.
TUC general secretary Paul Nowak said he hopes the protests and strikes will send a strong message to the Government about the anger felt by growing numbers of workers.
Education Secretary Gillian Keegan said she expects the “majority” of schools to remain open in England and Wales despite the teacher strikes, but added that “some will have restrictions” for different cohorts.
Meanwhile, NEU joint general secretary Mary Bousted said around 85% of schools are expected to be either fully or partially closed by the strike action.
Groups representing parents have released a joint statement in support of members of the NEU.
The groups say they share the concerns of educators that children’s education is being harmed because of a lack of qualified teachers and turnover of staff, and calls on the Government to engage with the union to negotiate a settlement and avoid the industrial action.
NEU joint general secretary Kevin Courtney said: “Taking strike action is very much a last resort for our members. They do so with a heavy heart because they cannot stand by and watch their pupils not receiving the education they deserve.
“Parents know from first-hand experience that children are losing out because of the chronic shortage of teachers. Often pupils are being taught by short-term supply, or staff who aren’t qualified in the subject they’re teaching.
Ms Keegan said she had been surprised to learn that teachers were not required to say in advance if they would be taking part in the strike.
She said the legal position will remain “under review”.
“It was a surprise to some of us that was in fact the law. I did write to everybody urging them to be constructive, to let their heads know, and I am sure may teachers will have done that,” she told Times Radio.
“There are discussions around minimum service levels, minimum safety levels, around hospitals, around rail – education is part of that Bill as well.
“We are hoping not to use that, we are hoping to make sure we continue with constructive discussions and relationships, but these things will always stay under review.”