NASA said class is now in session in orbit after a clean launch of space shuttle Endeavour.

With clear weather under a setting sun, Endeavour roared into space Wednesday evening on time as planned at 6:36 p.m. EDT.

The shuttle carried teacher-astronaut Barbara Morgan on a mission she said earlier she hopes will realize the unfulfilled dreams of her predecessor, Christa McAuliffe.

Cmdr. Scott Kelly led six fellow astronauts into space on the refurbished ship.

Morgan was initially an alternate in the teacher-in-space program with McAuliffe. After the Challenger disaster in 1986, she returned to her teaching career while still performing some duties for NASA. She has been at the agency training for missions since 1998.

First Lady Laura Bush called Morgan Tuesday morning to offer congratulations "one schoolteacher to another" and to thank her for her commitment to the space program and to education.

About 60 of the more than 100 original teacher-in-space candidates from two decades ago were on hand to watch the launch, just as they were when McAuliffe lifted off.

Endeavour's trip to the international space station for construction work features three planned spacewalks during the trip, with plans for a possible fourth.

It will be Endeavour's first flight since 2002. This mission, with the official designation STS-118, will be the shuttle program's 22nd visit to the international space station.

The construction will focus on adding a new truss that other units will be attached to on future flights.