The strikes, mirroring protests across continental Europe against government-imposed austerity, are the first in what unions have threatened will be a wave of action over pensions, an area where public sector unions are determined to fight.
Some 45 percent of schools were expected to close and another 40 percent were expected to partially shut, a teaching union estimated.
Air passengers could face delays because immigration officials joined a walkout that could involve up to 750,000 workers. Courts and government buildings were also affected.
Dozens of marches and rallies have been arranged across the country, and are expected to be generally peaceful.
Prime Minister David Cameron has condemned the strikes as irresponsible, saying that talks between unions and ministers have not concluded.
The government met unions on Monday and would meet them again next week, Cabinet Office Minister Francis Maude said.
“It is absolutely unjustifiable for parents up and down the country to be inconvenienced like this, forced to lose a day’s work when they are trying to go out to work to earn money to pay the taxes that are going to support teachers’ pensions,” Maude told BBC television.
But education union ATL said arguing that talks were going on was misleading. “Until the meeting last Monday we didn’t know there was going to be another meeting in July,” a spokeswoman said.
“It’s not something [going on strike] we do lightly. We’ve never done this before in our history. But the bottom line is we’re worried about what the government is going to do to the long term future of teaching.”
CHANGE NEEDED
David Cameron argues longer life expectancy means public sector pensions must change to ensure that they are affordable. The changes are part of government plans by 2015 to virtually wipe out a budget deficit that peaked at more than 10 percent.
Consequently, workers face higher contributions to their pensions and longer working lives. The proposals have hit a raw nerve at a time of wage freezes and job insecurity.
Union leaders assert that their members are bearing the brunt of a financial crisis caused by rich bankers.
“It is hardly surprising that public sector workers are on strike today,” said Brendan Barber, head of the Trade Union Congress (TUC) union body.
“They know that they are being asked to play an unfair part in deficit reduction. What adds insult to injury is that this is wrapped up in attacks on public service pensions as gold-plated, unreformed and unsustainable,” he added.
British right-wing newspapers backed Cameron, head of the right-leaning Conservative Party. The Daily Mail covered its front page with a “Defy the strike bullies” headline, while The Telegraph highlighted the “generosity” of current public sector pensions on its front page.
Even the coverage of left-leaning newspapers like the Guardian and the Mirror was not without criticism, highlighting the unpopularity of strikes among many private sector workers who say they have already had to deal with tougher pension terms and see no reason why public workers should be protected.
Analysts said the protests would challenge the government anew after it retreated on plans to restructure state-funded healthcare following lobbying from the medical profession.
Markets, which have reacted positively to government deficit-cutting plans, would take fright at any sign of a government climbdown over an issue like pensions.
Thursday’s protests involved about one in eight public sector workers, but other unions are gearing up for stoppages later this year if talks break down.
Some Britons sympathise with the strikers but others say they are being unrealistic at a time when households have suffered their biggest fall in disposable income for more than 30 years.
“The state of the country is pretty bad. They are a bit too focused on themselves,” said Michael Hayes, a railway manager from the London suburb of Chingford.
