A、Because she was arrested and imprisoned. B、Because a white mob attacked the school. C、Because she was afraid that the students

In the early part of the 19th century there were no schools in the southern states of America admitting black children to its free public schools. Some brave teachers ran secret night schools. Teachers who were found educating black children would be forced to leave town. The situation was better in the North and in 1787 the first African Free School was opened in New York City. This school and six others in the city began receiving public funding in 1824.
    When Prudence Crandall opened a school for black girls, attempts were made by local white people to burn the building down. Despite attempts to prevent the school from receiving essential supplies, Crandall school continued and began to attract girls from Boston and Philadelphia. The local authorities then began using a vagrancy law against these students. These girls could now be given ten lashes of the whip for attending the school.
    In 1834 a law was passed making it illegal to provide a free education for black students. When Prudence Crandall refused to obey the law she was arrested and imprisoned. Meanwhile, a white mob attacked the school and threatened the lives of Crandall and her students. Afraid that the children would be killed or badly injured, Crandall decided to close her school down.
    In 1849 there was a lawsuit against the city of Boston for refusing to admit black children to its schools. The case was lost but in 1855 Massachusetts legislature changed its policy and declared that "no person shall be excluded from a Public School on account of race, colour or prejudice."