St. Johnsbury Academy (SJA) is an independent, private, coeducational, non-profit boarding and day school located in St. Johnsbury, Vermont, in the United States. The academy enrolls students in grades 9-12. It was founded by Thaddeus Fairbanks, and accepts the majority of its students through one of the nation's oldest voucher systems. It has a sister school in Jeju Island, South Korea.