In 1984, President Regan announced the Teacher in Space Project to put a teacher in space to inpsire students to pursue interests in math and science. Out of over 11,000 applicants, NASA selected two candidates for opportunity: Christa McAuliffe and Barbara Morgan. Christa McAuliffe was supposed to be the first teacher in space on the 1986 STS-51-L Challenger mission, but unfortunately disaster struck. Morgan was later selected as a NASA astronaut mission specialist and flew in space on STS-118 in 2007. Her primary duty on that mission was operating the robotic arm to help add the S5 truss to the ISS, but she did spend about six hours teaching students from space.
In 2003, NASA announced the Educator Astronaut Project, which was similar to the previous Teachers in Space Project except that astronauts would undergo full training as mission specialists in addition to their teaching responsibilities. Joseph Acaba, Richard Arnold and Dorothy Metcalf-Lindenburger were selected as the first Mission Specialist Educators in the 2004.
Now, a new teacher astronaut program has been announced. The Teachers in Space Program will allow teachers to train on weekends and summers so they can keep their day jobs as teachers. The idea is to have a pool of teacher astronauts trained by the time the first commercial space vehicles start operating in a few years. The program is jointly sponsored by the Space Frontier Foundation and United States Rocket Academy. Applications for the first two "Pathfinder' astronauts are due December 4, 2008.