What was the matter with Rudolf Nureyev?

He sat on the stage of the Kennedy Center Opera House, sulking. The curtain, scheduled to go up at 8 p.m., was still down at 8:10, and it was going to stay down until Nureyev's Elvis Presley mug was found. Everyone else was dressed and in place, but Nureyev was still wearing his pink woollies and refusing to budge from a chair at center stage.

We knew what was the matter with him - we women forming a small knot, way back in the wings, where we were trying to look inconspicuous.

The problem was that Rudolf Nureyev has no stage-mother. He left his behind in the Soviet Union, and can't get her out.

Therefore, he got away with breaking nearly all of the rules that we stage-mothers insist upon before we allow our offspring to perform:

They must be present, properly dressed, and ready to perform at the exact time scheduled, even if they know that things will start late, or, as in the case of a rehearsal, that they will probably not be needed until hours later.

They are not allowed to swagger or expect any privileges, inside or outside of the theater. They must be courteous and cooperative at all times, even when others are going to pieces.

They must not eat or drink anything except in the canteen, when they are out of costume and not needed - and even then, being a show is no excuse for consuming junk food.

(There is also a rule that they must be familiar with the entire production, and perform their part, whatever it is, to the best of their ability. Even without his mother checking up on him, Nureyev managed this.)

But you see how essential a stage-mother is to anyone who spends time on stage. Our group that night consisted of the stage-mothers of children who were appearing with Nureyev (but in smaller roles) in the London Festival Ballet's "Conservetoire," and we discussed volunteering for the post of stage-mother to his poor orphan. We knew he might be difficult, but we thought he might be worth it. However, nobody offered because we were too busy explaining to our own children why they couldn't keep curtains held, or dressers to snap at or Elvis mugs. The moral they took from it was that if they worked very, very hard at ballet class, perhaps some time they could do all of those things.

Stage-mothering is, you see, a fine and exacting profession. What is the first thing you think of when you hear the term?

Pushy.

Well, yes, stage-mothers are pushed about a great deal. Standing in the wings, we knew we might be pushed back down to the canteen, where we might be pushed back up to the wings again and told to keep an eye on the children. We are also pushed around a lot by our children, who want us to take care of all their backstage things while simultaneously telling them how they looked on stage.

This particualr collection of stage-mothers did not belong to little stars or eeven necessarily kids with professional ambitions. Mine aspire to entering more lucrative professions, so that they will be able to afford to buy season boxes for all the opera and ballet that comes to Washington. What our children do, when they can get the jobs, is occasional brief dancing, but mostly tiny walk-on or crawl-on parts as animals, elves, sprites, royal pages or even children, in ballets or operas at the Kennedy Center Opera House and Wolf Trap Farm Park.

In addition to enforcing the rules, the stage-mother profession includes fringe benefits, such as the opportunity to share your cold-cream jar, to remove skateboards from corridors used by ballerinas whose legs you cannot afford to replace, to arrange playing cards for children who are trying to keep themselves occupied quietly but can't fix the cards because they are wearing paws on their hands, and to extract children from serious card games to which they have been invited by adult singers or dancers who should know better.

Why would any adult woman take such a job?

1. They are seething with frustrated desires to make glorious careers for ourselves. This is certainly true, but the careers we wish to pursue are our own, from which we have to take time off to stand around holding hairbrushes for little kids. I have yet to meet a stage-mother who had dreams of being a ballerina, but I have met an awful lot who dreamed of getting back to the office if the rehearsal would only end.

2. There is big money involved. The finances are that the children usually get paid $5 a performance and $3 a show. Naturally, they have earned this and get to keep it to invest in fancier skateboards and Dungeons and Dragons booklets. The big money is what the stage-mother lays out for parking, backstage meals, tickets so that the extended family can witness the child's two-minute appearance on stage, and records of the opera or ballet so that he can study the music beforehand, and reminisce afterwards. Then there are the continuing expenses attached to having a child who has developed a lust for quality entertainment. You can't park him in front of a television set any more or send him out to play in the alley. He wants to go to the opera with you, and spend his afternoons taking ballet and music lessons.

3. There is so much glory in it. The glory to the stage-mother is that everyone assumes her motives are ugly, and her mere presence flak. Far from being enchanted by children who love music and dance, the house management usually figures that they are natural-born troublemakers. Two child supers who went to the ballet as a birthday treat were stopped and bawled out by Kennedy Center Opera House personnel. When parents arrived to explain that the boys had tickets and had also been invited by family friends to visit the presidential box during intermission, the sole apology was, "Well, we recognized them as supers, so we thought they were harassing the people in the boxes."

4. They feel a sense of competition with other mothers and their children. A stage-mother's best friend is another stage-mother - during a show, often her only friend. Not only are other stage-mothers the only people who understand, but they share carpooling, canteen duty and other tasks. When an audition is announced, the telephones strart ringing among stage-mothers trying to encourage one another to participate so that no mother will find herself alone.

5. It leads to greater things. Being a child leads to puberty, which, for a child super, leads to unemployment. Just when a child has become really experienced, he becomes too big for the cute-children parts, while still too small for the adult ones. The stage mother becomes experienced and unemployed on the same schedule as the child, but in her case the enforced retirement is more appreciated.

Nevertheless, your conscientious stage mother keeps at it as long as her child asks her to, patiently enduring the demands on her time and the insults to her character. They do it to see their children learn not only what good music and dance are, but how much responsibility, hard work and discipline these require. When the school systems generally present the arts as something any child can do just by being "spontaneous" and "creative," the value of having your child watch Nureyev when he isn't sulking but is sweating it out at the barre, hour after hour, is worth all that trouble.

But besides all that educational stuff, you want to know the real reason? The deep down, honest, true motivation?

It's that your children are driving you crazy playing rock on the radio or record player all day, keeping it all blaring, and probably with the television set going as well. Mine just play their ballet records or turn on the opera. It doesn't matter what abuse I have to take on the outside; in return, I get a peaceful home. CAPTION: Picture, RUDOLPH NUREYEV, FAR FROM HIS STAGE-MOTHER IN "THE ROPES OF TIME."