It's back to school again for hundreds of thousands of pupils who missed lessons on Thursday as teachers stayed away to protest over pension changes.
At least 12,000 schools in England and Wales were closed or partly closed.
A strike is when a group of workers agree to stop working to protest against something they think is unfair.
As well as teachers, lots of other people who work for the government went on strike.
It was the biggest teacher strike for decades.
The teachers are angry because the government wants to make changes to their pensions, which they say will leave them worse off. But the government says it's fair to ask teachers to pay a bit more as people in other jobs do.
Some schools were completely shut, some were partially open and for some it was just an ordinary day depending on whether the teachers belonged to the unions which were striking - the National Union of Teachers, the Association of Teachers and Lecturers and the University and College union.
Other people who went on strike included some airport workers, people at job centres and courts, and civil servants, who work directly for the government.
What is a pension?
A pension is a pot of money you add to over your lifetime so you have enough money to live on when you're older and you retire, or stop working.
The government gives everybody in the UK a pension when they retire, but the amount you get each month depends on how much you've put in.
Some people have their own personal pensions too, so they have more money when they stop working.