From factmonster.com:
The Little Rock Nine, as they later came to be called, were the first black teenagers to attend all-white Central High School in Little Rock, Arkansas, in 1957. These remarkable young African-American students challenged segregation in the deep South and won.
Although Brown v. Board of Education outlawed segregation in schools, many racist school systems defied the law by intimidating and threatening black students—Central High School was a notorious example. But the Little Rock Nine were determined to attend the school and receive the same education offered to white students, no matter what. Things grew ugly and frightening right away. On the first day of school, the governor of Arkansas ordered the state's National Guard to block the black students from entering the school. Imagine what it must have been like to be a student confronted by armed soldiers! President Eisenhower had to send in federal troops to protect the students.
More here.