I knew a guy in college who came USA in 1976 as a "boat person," at the age of 10 - not knowing any english. 12 years later, he was valedictorian of our graduating class, on his way to Johns Hopkins Medical School.
One of my best buds growing up, he literally knew no English. Eventually he tired of people making fun of him at school so he learned English by having his neighbor read the newspaper to him every weekend then he read and spoke the words himself. He eventually became one of the researchers for the Antiques Roadshow.