When the movie theater slowly darkened and the film began, it was plain that the 500 students from Plummer Elementary School in Southeast Washington had been more than eager to see "The Wiz."

Five hundred shrill voices reached a high-pitched chorus as they read the names on the movie screen: "Die-ann-nuhh-Rossss," they chanted, ending in a shout that was followed by giggling and clapping.

When the music started-"Come on, ease on down, ease on down the road . . ."-the voice of Diana Ross blended into the voices of an audience of school children singing along full-blast.

A few of the children stood up and strutted in place laughing at themselves when the yellow brick road got to the bridge of Emerald City and the beat got thumping good.

All but 27 of the Plummer students recently went to see "The Wiz" at the Embassy theater on Florida Avenue NW.

The movie has been drawing long lines of mostly black children to its showing since opening in Washington in late October. On weekends, the movie has been a steady sell-out, night and day, with even nighttime crowds always 30 to 50 percent full of children, according to the manager.

All day Saturday and Sunday, rows of children advertise the movie's popularity with their age-group as they form a long line that wiggles from the movie theater door to the corner.

"The Wiz", with an all-black cast, has become such an institution that teachers and counselors at Plummer decided to use the movie as a learning tool, planning lessons around it before and after taking the students at the all-black school to the movie.

Some of the students at Plummer had seen the movie before the school trip.

"When I went the first time," said Cheryl Brice, 11, a Plummer sixth grader, "I stood in line a long time. It must have been two hours. The line went down to the corner and out of sight. After they showed it, they made everybody get out (of the theater) but I went in the bathroom and hid, and I went back in and watched it again."

Cheryl has seen the movie three times and plans to go again: "It's better when you go back, especially if you go with someone who hasn't seen it yet and you can tell them what's coming up. You know, you'll say, 'Watch this.'"

Plummer students paid $2.75 to charter buses and get into the movies at reduced rates. The movies usually costs $3.50 for adults and $2 for children under 12. Students who couldn't afford the trip had their fare paid by donations from teachers and counselors.

Parents of some of the 27 students who didn't attend had objected to the film's allusions to drug-introduced fantasies, scenes with prostitutes and the skimpy clothes on dancers in the movie, according to Ethel Lee, a pupil personnel worker Plummer who arranged the trip.

Angela Pettus, 12, a Plummer sixth grader who said the movie does show too many people who are not fully dressed, said the school could have arranged for students to see any popular film and got most of the students in the school to go.

"Movies," she said the day after the trip to "The Wiz," "are life and you know we're young and we want to see what's going on, like what's going on in life and movies can show you what life is all about, what people are doing that you don't see."

"And then," said Eric Munson, 12 who is in Pettus's class, "like a lot of people say 'Wow' when they see something freak in the movies and they figure 'I could do that too.' You know, go out and scare people or jump over cars, or they see people robbing banks in the movies so they go out and try it, try to be bad like in the movies. I don't do it. My brother and I used to be into doing the Kung Fu moves from the movies, but I stopped bcause I was always the one that got hurt."

After returning from the "The Wiz", every class in the school used the story as the basis for class work. In Ellissa D. Price's sixtg grade class, the students compared "The Wiz" to "The Wizard of Oz." Only one of three Plummers students who watched "The Wiz" with a reporter had seen "The Wizard of Oz." But almost half of the students in Price's class raised their hands when asked if they had seen the Judy Garland version of the story, which is shown on TV once a year.

In comparing the two films, the class listed the different settings for the movies-"a farm in Kansas" versus "The City of New York"-but agreed both films has the same message: "You have to look for courage, love, intelligence and confidence in yourself."

One of the major differences in the film for Price's class of black students was that the "Wizard of Oz" had an all-white cast and the cast of "The Wiz" was all black.

"As black people," asked Ruth White, a school counselor, "do you think we could have done what we did yesterday years ago? Do you think we could have gone to see black actors in a big, expensive film in a big theater? Do you think they would have let us do that years ago?"

"It means black people are moving up," said Rodney Bennette, a student. "Moving up and getting a piece of the pie."

In studying the movie, the sixth graders were supposed to sharpen their Competency Based Curriculum skills, a curriculum program used in the schools which spells out what abilities a student must have as he progresses from grade to grade. The class developed those skills by following directions correctly, reading about the film and its actors, using reference materials such as the encyclopedia and distinguishing between the fictiional characters in the story and the real lives of the actors who played the roles. CAPTION: Picture, Teacher Ellissa Price with students Cheryl Brice, Angela Pettus and Eric Munson. By Margaret Thomas-The Washington Post