After Chris Albers finished leading his classmates in the Oakton High School chorale through some vocal warm-ups Tuesday morning, he stared at the new tenor in the first row and shook his head in amazement.

"Gosh, you've got a great voice, man," Albers said.

Fairfax County Superintendent Linton Deck blushed but quickly regained his composure as he stepped to the conductor's podium.

"I'm an amateur musician. You're the professionals," Deck told the class. Then he offered a challenge to the room of well-trained voices: "Let's see how you sing."

Deck spent the entire day teaching choral music to students at Oakton as part of a program he designed to help school administrators remember -- and in some cases, discover -- what being in the classroom is all about.

The chief school administrator issued an edict late last summer that before the end of the 1980-1981 school year every administrator would spend one day in the classroom as a substitute teacher.

The command applied to everyone, including the superintendent.

"I thought it would be a good idea if I did it, too," he joked to the students.

For some school officials, like Deck, it has been many years since they have been in the classrooms on a regular basis. For others, the teaching experience is one they have never had.

"I think all of us need to remember what teaching is, and that it is a very demanding job," Deck told the students in his 10:25 a.m. class.

When Deck began teaching 30 years ago, the subject was biology. But he decided to embark on a new subject this week because of his well-known love of music.

"I've been a singer all my life," Deck explained as the first class, the most talented singers at Oakton, drifted into the room.

During the 50-minute period, Deck's mellow voice mingled with other tenors as he energetically directed the young singers through selections of holiday music.

With Deck at the helm, the 49-member select chorale sang almost flawless versions of "O Holy Night," the "Wassail Song," "Mary's Little Boy Child" and the "Hallelujah Chorus" from Handel's "Messiah." (The latter prompted several students to applaud themselves).

Deck also exhibited his skills as a captivating storyteller as he taught the class about the life of Handel in the 18th century.

"Handel was the Richard Rodgers of his time," Deck told the class after they finished singing part of the exhausting oratorio. "No one took him seriously as a composer of sacred music because he spent most of his time composing music for plays and parties. . . ."

When the bell rang for lunch, the young singers did not rush to the cafeteria but stayed behind to thank the superintendent.

"He was neat," said junior Laura Duffy as she waved to Deck on the way out of the room.

"He is an excellent conductor," said Albers as he collected his books. "I was surprised he was such a talented singer."

Deck was just as pleased with the students.

"They've been wonderful. If I had it to do all over again, I might like to do something like this . . . but who knows?" he shrugged.