The richest countries in the world use their native languages as their medium of education at least up to the end of high school. 

Even Korea and Taiwan, with populations of 51 million and 25 million people respectively (less than the number of telugus in the telugu states) have much higher per capita income than India and use Korean and Chinese as their medium of instruction. China is now a superpower in Artificial Intelligence, and high-end technical work happens in Chinese. Most Europeans (look at Italy, France, Germany, and wealthy countries like Denmark, Norway, Sweden, Finland and even Iceland) can speak 2 or 3 languages, including English, but have most of their education in their native languages and are extremely fluent in their native language.