In many countries where a language unique to that country is spoken such as Finland or Turkey students are first taught English and then courses from then on use English language textbooks. I can remember buying a beef sandwich from a street vendor in Istanbul and finding that it was wrapped in a test paper written in English. As long as most textbooks are in English and not in peculiar regional one such as Punjabi English will remain the number one language. There is an exception. The number one language is Hindustani. Mathematics uses a number system that comes to us from India by way of Arab traders many centuries ago. Pick up any paper currency and you can find how much it is worth due to Arab-Hindustani numbers.