Joseph Merlino peeked out from behind the doorway, as a schoolboy might just before committing a dastardly deed.

In an instant he was in full view, poised like James Bond, both hands gripping a water pistol. He fired and, with 007 accuracy, hit his mark. Two tables and a chess board away, Julie Krone was dripping wet.

Meanwhile, Greg Hutton reclined on a couch, trying to decide between a midday snooze and "Three's Company," which was on the TV set in front on him.Suzanne Somers was losing this battle.

Three pinball machines and one pool table to the east, Kenny Black has Charles Hinojosa Jr. at game point on the Ping-Pong table. At 5 feet 3 and 105 pounds, Black easily stood out in the room full of teenagers, who might have been at a summer camp.

But a moment later Pasquale Razionale walked in, carrying his whip, wearing his white baggy pants. It was 12:30 p.m., 30 minutes until post time. Soon, the fun would end in the jockey's room at Camp Pimlico.

At 1 p.m., this team would not play Camp Summertime in a game of softball.

They would begin playing each other in a very competitive game of one-on-one-on-one-on-one.

Pimlico Race Course was about to open for business.

Horse racing is as much a business as it is a sport, beginning each day with the exercising of the horses and ending long after the last race. The race track is not considered a proper place for teen-agers. Unless, that is, you're a jockey.

"Around here, it's not how old you are, but how long you have been riding. I worked my first horse out of the gate when I was 9 in Utah," said Black, who, at 17, is Pimlico's youngest journeyman. He also is fourth in the jockey standings, despite missing four weeks after breaking his collarbone in the fall that paralyzed Sammy Boulmetis Jr.

Black's 13-month apprenticeship ended March 12. "I won 270 races with the bug (the asterick next to an apprentice jockey's name in the program)," he is quick to point out.

"The older guys (jockeys) are more settled down and not as ambitious as the younger ones," Black said. "They have to support families. The younger guys have ambitions. I want to be the best jockey in the world. Younger riders may not always want to ride in Maryland. They may want to go to California or somewhere else real big."

Such ambitions create competition among the younger jockeys.

"It's kind of hard. One minute we're all together and the next minute we're one against one," said Krone, 17, who like Hinojosa, Hutton, Merlino and Razionale, is an apprentice. She also is one of four women who ride regularly at Pimlico.

"We are all competing," said Hinojosa, 19. "When you win three of four races and get hot, people notice you and you get good mounts. That's important when you're young."

"There is a real competition between the younger jockeys," said Hutton, 18. "But the fine line is results. You have to win."

Said Black: "We are friends, but we are all rivals. Sometimes, your trainer will tell someone that your friend can't ride. Well, you don't like that, but it is part of the game. You have to get good mounts."

You also need good press. Upon hearing that a reporter was in the room, these young jockeys crowded around, as if the writer were a Good Humor man and they were children, allowance in hand.

"Publicity is important. People see your name and they know you," said Merlino.

"We fight for all the publicity we can get," said Black. "It's part of the game."

Hutton said simply, "I need a good story."

What about school?

"I think school is a joke," said Krone, whose father is, of course, a school teacher in Michigan. ("He loves it that I'm a jockey," she said.)

"It's wrong for someone who already knows what they want to do in life to have to go through with it. You pass a class. Big deal. On the track you work hard and get hot and dirty."

Krone left school after the 11th grade and now is taking correspondence courses. "I have to take geography, history and two math classes," she said, emphasizing the agony of double duty in arithmetic. But she also noted, "I don't know too many 18-year-olds who are making between $2,000 and $5,000 a week."

Hinojosa is the only one of these jockeys who has graduated from high school in the standard manner.

"I almost didn't go back for high school after I started working on the track," he said. "School didn't matter. But I went back and most of the time in class I spent daydreaming about riding."

Hinojosa didn't turn to riding on a whim. It was Charles Hinojosa Sr., his father and a long-time jockey, who showed him the way during his summertime vacations from school. "I guess I was bred for this," he said. "I'm looking forward to the day I ride on the same card as my dad."

Hutton came from Canada, where he turned toward riding and away from school after the 10th grade. He has considered correspondence school, but has little time. "I get up and out to the track by 6 a.m. and I'm not done until after 6 p.m.," he said. "I have no need for college. You don't have to know your mathematics to ride a horse. You only need natural talent. Either you have it or you don't."

Merlino is from South Philadelphia, "the bad part of the city." He did not finish high school, either. "When I was little, maybe 14, I used to be in a gang and we hung out on the street corner. I got away from that and I don't want to go back. If I wasn't riding I would probably be working in construction like some of my friends."

Razionale was born in Italy. His family moved to Boston in 1964, when he was 4. He finished 10th grade and says, "Once my career gets going I will finish up." Razionale is living at Pimlico with his agent. "It's a nice place. We got a great deal because we have a TV, a stereo and we play chess."

All of these riders live with an agent, a friend or someone connected with the track. Although none admits to homesickness, it seems likely some of these teen-agers miss home-cooked meals and clean socks. "I call home at least once a week," Krone said.

Black has been riding the longest. Perhaps that is why he has advanced the furthest. He talks of races and tracks like a rock star would of concerts and pavillions, recitng the names as though they all run together in one long engagement.

"My dad was a rider and I grew up on fair tracks out in the bushes and on the farms," he said. "I've ridden in California, Florida, Illinois and Utah. If you're small and your dad was a rider, than you become a rider." His 12-year-old brother is following suit. "He's about 4-foot-7 and he weighs 65 pounds." Black said. "He used to want to be a surgeon, but now he wants to be a rider."

Black passed a general equivalence test after ninth grade, meaning he earned credit for a high school diploma. Because his family moved so much, Black said he attended 15 different schools. His parents divorced when he was 12 and Black went with his father because "my dad could teach me about riding.

"All my friends are at the race track. I never went to any school long enough to make any real friends there, especially in my later years."

Later years?

"Yeah, you know sixth, seventh and eighth grade. All my life I have wanted to be a rider and I hope to ride until I'm 70."

Most of these young riders have favorite jockeys, just as handicappers have favorite horses.

"Carlos Lopez. He's the best in the country," said Joseph Merlino.

"Robin Platts and Sandy Hawley. Hawley may not look that good, but he wins," said Greg Hutton, choosing two Canadian countrymen.

"Willie Shoemaker. Anyone who wins 8,000 races can't be too bad," said Julie Krone.

"Angel Cordero. He'll do anything to win a race," Kenny Black said.

Pasquale Razionale paused before responding. "Truthfully, I just watch the older riders here like Mario Pino, Ron Franklin and Bill Passmore. They have got experience, and if you watch them, you learn. Some of us are very young, you know."