Say goodbye to "Mary Had A Little Lamb" and "swing Low, Sweet Chariot." Say hello to the Polymoog, the ARP and Sel-Sync. the electronic revolution is about to invade the music class, and the high school band and grade school choir will never be the same.

That may not have been what the 4,000 music teachers who attended this year's Music Educators National Conference (MENC), which ended yesterday after four days of clinics, concerts and panel discussions at the Sheraton Park and Shoreham hotels, wanted to hear. But the evidence was all around them -- and not just in the form of the synthesizers and other electronic devices that popped up amidst the more traditional trombone violin, guitar and piano displays.

It was the workshops that seemed to offer the most surprises. At a demonstration called "Eletronic Music in Real Time: The Synthesizer Ensemble," curious elementary and high school music teachers heard a four-man, all-electronic band perform. And at the "Electronic Music Class and Laboratory Management" clinic, they heard, to the amazement of some of them, a sophisticated piece of "musique concrete" composed by an eight grader on Long Island.

The "electronic music explosion," as Otto Luening, the Columbia University professor and electronic composer who was MENC's chief speaker, calls it, is part of an attempt by music educators to adjust to the times. School boards all across the country, squeezed by budget problems, are wondering if music isn't a "frill," so music teachers, seeking greater relevance, are injecting pop music, jazz, ethnic music and electronic music into the curriculum.

"Musicians are by nature a rather conservative bunch," says Robert Klotman, chairman of the Music Education Department at the University of Indiana and current president of MENC. "Our studies have shown that it takes 50 years for a new idea to permeate the American shcool system.

"But in the last seven or eight years, we have had to accomodate dramatic changes. We no longer can consider traditional Germanic music as the only form of music. We've got to look into things like electronic music and the music of Afro-Americans and Spanish-Americans. It's the whole 'Roots' thing."

For their part, the 3,000 music students who performed at the conference were fascinated by both the music of the past and the music of the future. The booth displaying traditional African and Asian percussion instruments may have been exceeded in popularity only by the Norlin Music Company's Polymoog synthesizer --than six months and costs $4,495.

"Nothing fazes these kids," says Herbert A. Deutsch, chairman of the Hofstra University Music Department and an electronic music consultant to school systems across the country. "They have no qualms whatsoever about operating a complex piece of machinery like the Polymoog.

"They've been brought up on the synthesizer, so to them it's like any-other musical instrument. We're producing a generation of synthesists."

Deutsch believes that the trend toward electronic music in the classroom can be traced back to Walter Carlos' "Switched-On Bach' album, released in 1969. "The schoolteachers dug it," Deutsch says, "and told themselves 'now we'll be able to get classical music to the kids.' The teachers thought that the kids would love Bach, but what happened was that the kids fell in love with the synthesizer."

They have been encouraged in their love of the synthesizer by the electronic laboratories and studios that have been springing up in grammar schools and high schools across the country. Some of the music teachers attending the MENC symposia reported having wah-wah pedals, phase shifters, multi-track mixing machines, tape recorders and as many as four synthesizers at their disposal.

"It's the middle schools, grades six through nine, where most of the work in electronic music is going on," reports Deutsch. "Even the districts that can't afford a big laboratory in every school already have one or two synthesizers that go from school to school for mini-sessions that encourage the kids to explore sound."

"In 20 years time," says Tony Messina, a junior high school music teacher at the Wading River Middle School in Shoreham, N.Y., "you're going to be hearing synthesizers and punched-out music all over the place. The day of the traditional orchestra is over. Electronics is the wave of the future.

"What I'm doing is trying to prepare for that. I'm getting my kids ready for the 21st century."