He threw a look at momma and swished his racket disgustedly in the air. "Leave," he hissed at her. He had just double-faulted into the net. Another point was blown. "Leave," he commanded again, and gestured to the clubhouse.

To hurry herself away from the presence of her twitting 13-year-old tennis star son was pain enough for the mother. The extra hurt came when she looked at the others in the courside seats to see if we had noticed her son's distemper. We had.

Almost everything was noticed at the first Vero Beach Open Junior Tennis Championship. The town had been waiting 14 months for the Florida Tennis Association to sanction a junior tournament for the area. Open dates are hard to come by.

But not talent. Florida, along with California, is the nation's breeding ground for tennis stars. Of 46 American women in the first round of the recent U.S. Open, nearly half were from the two states. In Florida, junior players compete in a statewide tour in which parents can be paying $5,000 yearly in travel expenses to get their children to the tournaments. That excludes lessons. A teaching pro says that most 12-year-olds on the junior tour have at least a $5,000 forehand. To wait longer or invest less is to risk stunted development.

All of this should seemingly rate a cheer for the family of man, as Florida and California have perfected it. But the price of early greatness -- acquiring an underspin cut shot at 10, an American twist serve at 11, a smash at 12 and a pro contract at 14 -- seems to be producing a courtful of boorish and self-absorbed loudmouths like John McEnroe and Jimmy Connors.

The excesses of parental involvement in Little League baseball have been well reported. But those of junior tennis offer a more detailed picture of what adults can do to take childhood away from their children.

Tennis, like other individualized sports, ought to be a game at which mastery is reached in adulthood, when the self can maturely handle the pressures of big-dollar competition. In tennis, let a 4-year-old swat a few decent shots over a net taller than he is and some daft parent will be hauling him off to a pro for lessons. There wil be dreams of Wimbledon, but the astuteness of Englishman Cyril Connolly ought to be given center court: "Whom the gods wish to destroy they first call promising."

At the Vero Beach tournament, talent-rich amd personality-poor McEnroes of tomorrow were on view. Promising tourney-tested juniors walked onto the court morose, played sullenly and walked off-winners and losers-with no trace of joy. Most were children of privilege who have been blessed with health, talent and country-club tans. Yet they are as sourlooking as gravediggers.

In junior competition, the children are forced to internalize the pressures on them. But it comes out eventually in erratic emotionalism: ordering mom from courtside, berating the umpires, banging loose balls into the net, leaving the court in tears.

The kids shouldn't be blamed. They will practice like machines for fourand five hours a day to win a tournament in their age group and will adopt airs of metal toughness. But inside their parentally programmed bodies are feelings about games and sports that all kids, being God's true fun-lovers, instinctively have in their hearts. Children don't want to become technique oriented. Competitive tennis, a sport of technique and cunning, is the last game that should be imposed on children.

the kids' problem is that they aren't yet steely enough to tell their hovering parents to cool it. Tennis pros even have difficulty dealing with pushy parents. Maybe it's only in fiction that controls can be found. In "Metamorphoses," John Cheever told of a kind of children who "are a truly pure and innocent breed, and it would never cross their minds or their hearts to upset or contravene the plans, dreams, the worldly triumphs that their elders hold out for them. It seems to be the hand of God that leads them to take a pratfall during the tabeaux at the debutante cotillion."

Or lose in the first round of the Vero Beach, or Coral Gables, or Boca Ration junior open. And then mom and dad are disgraced. The hope is that the loss will free the child.