The National Honor Society is a high school student organization, funded and sponsored by the National Association of Secondary School Principals; it has chapters in the United States and U.S. territories, as well as in Canada, and was the first U.S-wide honor society, though many local or regional honor societies predate it. It was founded in 1921 by Dr. Edward Rynearson, principal of the Fifth Avenue High School, Pittsburgh, Pennsylvania, and had more than a thousand chapters by 1930. (In 1929 the middle school spin-off, the National Junior Honor Society, was also started by the NASSP.)

NHS says its aims are to recognize high school students "who have demonstrated excellence in the areas of Scholarship, Leadership, Service, and Character." A National Council of NASSP members is appointed to establish standards for all chapters and select recipients of the National Honor Society Scholarships which has been given out since 1946.

NHS Members must be in grades 10-12, have a B average or equivalent, and fit some standard of service, leadership, and character (the web site did not define the standards used in these categories). Members are inducted into the Society at an induction ceremony, and each chapter is involved in service projects such as fundraising. The national organization also holds an annual conference and summer leadership camps.

Their web site currently emphasizes that despite rumors to the contrary, they do not deny membership to pregnant students or single mothers, and notes that if they did it would violate Title IX provisions prohibiting sex/gender discrimination. (I'm willing to bet that the founder would have excluded pregnant students on character grounds.)

From the high school student point of view, NHS is often just like other student organizations. People join because it looks good on college applications, but to quote my classmate Jaime, who along with me qualified but did not join, "All they do is sell candy. What is so honorable about that?"

Source: http://dsa.principals.org/nhs/