Sounds bloody amazing. I think all kids should have the chance to do this! Travelling the world for a year! 😄 Not sure how the practicalities would stand, and they would have to be pretty smart academically. We had a 5 week trip to Canada and America when DD was 9, mid Feb to Mid March, so one week did include half term, so she officially only lost 4 weeks.
The school allowed it - and called it authorised absence, because she was quite academic and had the Maths and English skills of a child of 12-13. (Sorry for stealth brag!)
This was 20 years ago, not sure if it would be allowed now. By the time she was 12-13 the secondary school was very strict, and got really shirty with us when we took her to EuroDisney for 4 days - when she was 12 (with her 9 y.o cousin,) and she only lost 2 school days then!
DD still talks about her amazing trip to America and Canada though, and she absolutely loved it. She spoke to New York cops, and taxi drivers, and went to many New York sights (Manhattan, Empire State Building, Macys, Bloomingdales, Plaza Hotel, Times Square, Central Park, Queens, Brooklyn, all sorts.) And she experienced American life for 2.5 weeks.
We also spent 2.5 weeks in Canada.
We saw Niagara Falls, Buffalo, Lake Ontario, Lake Erie, Lake Michigan, and Chicago, Detroit, Milwaukee, and Chequamegon–Nicolet National Forest, and Montréal, Toronto, and Quebec City. It was such a wonderful memorable time for us all. But it was only 4 weeks lost schooling. Not sure how taking children out for a year would work. But some do it, so I guess it can be done!