* Lack of Centralized Database: There's no global organization tracking this specific information for every school.
* Variability in Definition: What constitutes a "school uniform" can vary widely. Some schools might have strict dress codes, others have more relaxed guidelines.
* Data Collection Difficulties: Gathering this data across diverse countries and educational systems would be a massive undertaking.
While we can't give a number, it's safe to say that a significant portion of schools globally utilize some form of uniform or dress code, though the prevalence varies greatly by region and country.