Christa McAuliffe, a high-school social studies teacher from New Hampshire, was the winner of a nationwide competition to be the first private citizen to fly aboard a space shuttle. She was 37 years old. Students always packed Mrs. McAuliffe's classes at Concord High School because of her enthusiasm and ability to make dry subjects come alive. And so last July, when she was selected as the primary candidate to be the first teacher in space, broadcasting lessons to millions of people across the country, her students broke into applause. ''She's perfect,'' said Ann Tousignant, 18, one of her students last year. ''She brings lessons down to earth.'' Today Mrs. McAuliffe and six crewmates were aboard the space shuttle Challenger when it exploded shortly after launching from the Kennedy Space Center here. Mrs. McAuliffe had looked forward to the mission with enthusiasm. ''I think just opening up the door, having this ordinary person fly, says a lot for the future,'' she said at a recent news conference. ''You can always equate astronauts with explorers who were subsidized. Now you are getting someone going just to observe.'' ''And then you'll have the settlers,'' she continued. ''The space station is not too far down the road.'' Although interested in the space program in her youth, Mrs. McAuliffe spoke of having no female role models. ''It fascinated me that rocket ships were going up and that something could escape gravity or get into orbit,'' she said recently. ''But it was never anything that I aspired to. When I was young, women did not fly in space.'' Sharon Christa Corrigan was born in Boston on Sept. 2, 1948, to Grace G. and Edward C. Corrigan, and grew up in Framingham, Mass., a suburb of Boston. According to her father, a retired accountant who worked for General Telephone and Electronics, Christa was always energetic and goal-oriented. She attended Marion High School, a small Roman Catholic school in Framingham, and was an all-star softball player. She earned a bachelor's degree in American history and secondary education from Framingham State College in 1970, married Steven James McAuliffe, whom she had met in their sophomore year, and moved to Maryland, where she taught high school English and American history. In 1978, she received a master's degree in education from Bowie State College in Maryland and moved with her husband to Concord, where he established a law firm. At Concord High School, Mrs. McAuliffe taught law, economics, American history and a course she developed entitled ''The American Woman.'' In her history courses she emphasized the impact of ordinary people on history, saying they were as important to the historical record as kings, politicians or generals. After President Reagan announced plans for a citizen-participant space program in August 1984 with a teacher as its first passenger, Mrs. McAuliffe was one of 11,000 applicants. ''Just as the pioneer travelers of the Conestoga wagon days kept personal journals, I, as a pioneer space traveler, would do the same,'' she wrote, describing her proposed space project. ''My perceptions as a non-astronaut would help complete and humanize the technology of the space age,'' she added. ''Future historians would use my eyewitness accounts to help in their studies of the impact of the space age on the general population.'' As do all astronauts, Mrs. McAuliffe studied emergency procedures for dealing with space accidents and emergency landings. She also had to study a stack of training manuals and learn the intricacies of life in orbit, and experienced weightlessness in a space agency training jet. Through it all, she kept her sense of humor and enthusiasm. For good luck on the Challenger's flight, she took with her a stuffed frog, ''Fleegle,'' that belonged to her 9-year-old son Scott. In the flight, Mrs. McAuliffe was to have taught science lessons on television over the Public Broadcasting Service to school children across the country. After the flight, she was to have stayed with the space agency until September, speaking to students and civic groups around the country about her experiences. ''I feel a great responsibility and excitement this year that I'm representing my profession,'' she said. ''I'm hoping that it's going to elevate the teaching profession in the eyes of the public and potential teachers out there. One of the secondary objectives of all this is that students are going to be looking at me and perhaps thinking of going into teaching as a profession.'' Besides her husband, parents and son, she is survived by her daughter Caroline, 6; two sisters, Betsy Corrigan of Venice, Calif., and Lisa Bristol of Marlborough, Mass., and two brothers, Steven Corrigan of Salinas, Calif., and Christopher Corrigan of Framingham.