* Number of applicants: Some schools are incredibly selective and receive thousands of applications, making them popular in the sense of high demand. However, this doesn't necessarily mean they are popular with *all* students.
* Global reputation: Certain schools, often private and boarding schools, have strong international reputations for academic excellence and may be considered popular among students seeking a prestigious education. Examples might include Eton College (UK) or Phillips Exeter Academy (USA). However, their popularity is geographically skewed.
* Student satisfaction: A truly popular school might be one where students are happiest and most engaged. This is difficult to measure on a global scale.
* Social media following: Some schools might have a large social media presence, but this is not necessarily reflective of global popularity.
In short, the concept of "most popular high school in the world" is subjective and lacks a quantifiable metric.