Earlier this year, schools around the world closed their doors.
By early April, nearly 1.5 billion children and young people were at home because of the coronavirus pandemic.
More than 60 million teachers were out of the classroom as well, according to UNESCO.
But as the weeks and months passed, countries began easing out of lockdown and restrictive measures.
Schools began to reopen.
Social distancing, masks, 'bubbles', temperature checks, blended learning and regular handwashing have all become features of Covid-19 classrooms.
As Ireland's 4,000 primary and secondary schools begin reopening, we spoke to five Irish teachers working overseas about their back to school experience.
Marcus Concannon is a science teacher in Bangkok.
"We went back to school on 1 July in Thailand. In the classroom, the desks have perspex around them, so the pupils are self-contained, like a cell.
"Students don't have a problem wearing masks and we do lots of handwashing. It's gone very well and we haven't had an outbreak for 84 days," he said.
In Abu Dhabi, the capital of the United Arab Emirates, John O'Boyle's school has adopted a "blended learning approach".
"Our class groups are divided into two. Only 15 pupils are allowed in the class group at any one time. Group A attends school on Sundays and Mondays, while group B works from home.
"Meanwhile, group B attends school on Tuesdays and Wednesdays, while group A works from home. Both groups work from home on Thursdays," he explained.
Mary Johnson returned to her school in Amsterdam in the Netherlands last week.
"Students here don't have to social distance. But there's a line on the ground in every classroom which teachers and students are not allowed to cross during lessons.
"We also have to wash our hands as we enter and leave the classroom. The windows and doors are open at all times. We also have to wear face masks in corridors, but not during class," she said.
Liam Printer teaches Spanish at the International School of Lausanne in Switzerland.
"Students, teachers and everyone in the school buildings have to wear face masks from the age of 12 upwards," he said.
"There's a 2m area around the teacher's desk which students aren't allowed to come into. If you're in that area and you're teaching, you can remove the mask if you maintain the 2m gap. I'm glad about that because as a language teacher, students being able to read your lips and body language is really important."
In Luxembourg, primary school teacher Emma Nelson says several reopening initiatives have been a success.
She said: "We've had lots of emphasis on hand sanitising, social distancing and temperature checks. Our kids wore masks around the corridors and in and out of school.
"We also didn't have any homework, which was a way to reduce the number of items coming in and out from home."
Asked what advice she had for teachers and pupils returning to school in Ireland over the next few days, she said: "Be safe, be positive and be kind. I wish you the very best of luck."