How can I describe what year of high school a student is in that can be understood by people all around the world?

You can’t. You have to explain to them how your particular school system works first. It’s not even the same in different parts of the same country.

In general, in the United States, high school is grades 9 through 12. In my particular home town, elementary was Kindergarten through 4th, middle school was 5th and 6th, Jr. High was 7th and 8th.

And even then, just 5 years before I got to the High School, Jr. High was 7th-9th, High school was 10th-12th.

It’s better to just say what grade they’re in. Not what year of a particular division of the school system.

You could say “I’m in the first year of the four years of high school” or “I’m in year nine of the twelve years of public school.”

Thanks, I feared there’d be no simple explanation. :P

Year x of y, where y is the total number of years, and x is the current year level.

Note about UK schools: We have primary school and secondary school. These have “Years” labeled from 1–6 for primary school and 7–11 or secondary school. After secondary school you can chose to have sixth form education which are known as Years 12 and 13.

You can work out what ages you should be by just adding 4–5 to the school Year. So for people in year 11 they would be 15–16 year olds.

I think using age grouping is much better than giving labels when talking to people unfamiliar with your school system.