Duolingo is created in such a manner that it swiftly assesses a candidate's aptitude. The exam is adaptive, meaning that if you properly answer one question, the following one gets more difficult, and so on. It evaluates a candidate's ability to listen, talk, read, and write. And, to be admitted to the Harvard Extension School, you must show confirmation of your English proficiency with a minimum score of 125 which is no older than two years old.