Undated (AP) _ Students glued to TV sets in school cafeterias and auditoriums nationwide erupted in cheers, tears and applause as they watched Discovery flawlessly lift off the launch pad.

''I had my fingers crossed the whole time,'' said Christy Holt, a fifth- grader at Julian Harris Elementary School in Decatur, Ala., where about 80 children watched the launch Thursday.

The school is on McAuliffe Drive, named for Christa McAuliffe, the Concord, N.H., teacher who was killed in the Challenger explosion on Jan. 28, 1986.

The successful launch of Discovery came as a relief to teachers who had to explain to their students what had happened 32 months ago.

Students of the next American teacher in line to fly aboard a shuttle watched the liftoff at their school in McCall, Idaho. Their teacher, Barbara Morgan, was in Florida for the launch as she was for Challenger.

''We never had any doubt about putting the kids in there again,'' said McCall-Donnelly Elementary School Principal John Wall. ''We just needed to do it. I'm relieved everything went well. I was more worried than I wanted to admit.''

Although the National Aeronautics and Space Administration has not set any date for civilians to return to space, Morgan was enthusiastic about the possibility of flying aboard a shuttle.

''When they're ready to send me, I'll be there,'' she said.

At an Ohio school with a library named after Challenger astronaut and alumna Judith Resnik, students who felt a special loss from the Challenger disaster were absorbed by Discovery's launch.

''Suddenly, everyone became very observant,'' said Dennis Woods, principal of Akron Firestone High School.

''That last 10 seconds, the kids were counting it off. When it left the pad, there was a round of applause. Then there was a period of ominous silence, as the kids remembered the Challenger. When the rocket booster was released, that brought on another round of applause.''

Students at Challenger Junior High School in San Diego watched the liftoff on television monitors in 30 classrooms. The students earlier sent goodwill messages to the Discovery crew.

Seventh graders in Rosemary Eskridge's science class at Eisenhower Middle School in Oklahoma City were sophisticated enough to hold their cheers until Discovery separated from its booster rocket. It was at the separation stage that Challenger blew up.

Donna Hanebut, a third grade teacher at Uintah Elementary School in South Ogden, Utah, said ''there was lots of excitement and apprehension'' among students she had led on an expedition last summer to the U.S. Space Camp Training Center at Marshall Space Flight Center in Huntsville, Ala.

At the camp, more than 100 students from grades two through high school assembled at a pep rally for the launch.

Chere Linwood, a third-grader from Davis Hills School, was among those at the Space Camp for the liftoff and said she was scared. ''My mama told me to pray that they wouldn't die,'' she said.

Students at Dick Scobee Elementary School in Auburn, Wash., watched the liftoff in tense silence.

''There was a lot of anxiety,'' said Principal Don Lapinski, whose school was renamed for the Challenger pilot. ''My stomach was in a knot, too.''

Pink-clad students at Washington Elementary School in Willmar, Minn., where Discovery astronaut George ''Pinky'' Nelson attended fifth and sixth grades, counted down final seconds to liftoff and then ''the entire student body started clapping,'' said Principal Paul Olberg.

Jean Bendezu, a seventh grade science student at Miami's Carver Jr. High who plans to be an astronaut, said he was impressed with the takeoff.

''Now I want to go to the university and learn about astronauts, space and gravity,'' he said.

But TV screens were dark in at least one school.

At the Kimball School in Concord, N.H., where McAuliffe's two children attend, Principal Clint Cogswell said no classes watched the launch. He said he and his staff feel a duty to shield the McAuliffe youngsters - Scott, a sixth grader, and Caroline, a third grader - from reminders of the tragedy.