Spencer Liang doesn't remember exactly when it happened or specifics of the match, but she can recall the frustration that boiled up that day on the tennis court years ago.

Engaged in a tight battle against another elite junior player, Liang hit a momentum-changing winner that landed well inside the court for a chance to advance to the next round of a competitive Mid-Atlantic tournament. Her opponent, however, ruled the ball out.

Liang fumed and argued against what she felt was yet another egregious call, one of several in the match she believed her opponent had made to gain an advantage. But it was no use. The call stood. Eventually, Liang decided to take matters into her own hands. On the next on-the-line shot her opponent hit, Liang raised her index finger to indicate the ball was out — even though, in reality, it was too close to tell. This was payback, Liang figured, her way of leveling the playing field.

"I just felt really guilty about it after," said Liang, a former elite junior and collegiate tennis player. "I only did it probably when I was younger, when I didn't really know how to handle that stuff well. Then I learned from it. I knew I didn't want to win that way."

The 22-year-old Potomac, Md., native would go on to earn numerous sportsmanship awards over her distinguished career that culminated in an NCAA team championship with Florida in May, garnering respect from her peers and coaches. But the lesson she learned that day highlights the hypercompetitive nature of junior tennis, and an unwelcome reality: The sport, once lauded for its sportsmanship, is littered with accusations of widespread cheating at the youth level.

The conditions junior players find themselves in form a potent combination. Highly ranked players are expected to win. Their parents invest thousands of dollars in travel and coaching per year. And most of the time, players, with the knowledge of those two important factors, are required to make their own line calls and keep score in the midst of intense competition.

"The cheating in the game is, to me, worse than ever," tennis legend and TV commentator John McEnroe said during a recent ESPN conference call. "I guess the stakes are higher. It's a shame that these poor kids feel so much pressure. They cheat in practice at the club when we play. It's crazy. That is an issue that definitely has to be dealt with."

The discussion of cheating in junior tennis is hardly new. Tennis Hall of Famer Andre Agassi, 47, writes in his 2009 autobiography about being cheated by a fellow American player during a 10-and-under tournament. McEnroe, 58, also reflects in his 2002 book about his experiences with being on the receiving end of bad line calls as a junior.

But the extremely high costs of tennis and pressures of getting a college scholarship are more pronounced than ever. Program fees for the Junior Tennis Champions Center in College Park can cost about $40,000 a year, and that's not including equipment, tournament fees and travel expenses.

"I just think, whether the kid realizes it or the kid is being told, there's just more and more pressure, time, money going into their training, and that will, of course, bleed out on the tennis court," said Vince Pulupa, who coached Liang for several years.

Added Liang's mother, Velma Lee: "I put a lot of pressure on her to win, not to cheat, but to win. . . . It's difficult for all parents to travel to tournament to tournament and pour all this money."

Liang was ranked in the top five nationally as a junior and played for Harvard before transferring to Florida before her sophomore season, and she is now working at a commercial real estate finance firm in Bethesda, having experienced the highs and lows of competitive tennis.

"When you don't perform in one tournament or two tournaments, you just feel everything is falling apart and that you're not where you should be," Liang said. "The pressure is just really insane. . . . And if you don't [play well] constantly, you feel like you're going to fall behind right away."

At the center of controversy is often the fact that tennis at the youth level is one of the few sports in which athletes are making their own calls. Umpires are rarely stationed at every court, and there are matches at the high school level that have no officials.

"Think about it — can you imagine football players throwing a flag on themselves?" former Virginia men's tennis coach Brian Boland said. "Or batters calling their own strikes? Or how about in soccer, kids get to decide when to give themselves yellow cards? It's a testament of the integrity of our sport. . . . There's nothing negative about that, except you have a population who struggle to manage their competitiveness."

More than once, said Boland, who is now the head of men's tennis for USTA Player Development, he decided not to recruit "an extremely talented player" because of ethical concerns that included a reputation as a cheater.

The perceived amount of cheating that goes on in the game can also impact players' social lives.

When Reilly Tran, a sophomore at Marshall High in Northern Virginia, started playing tennis at age 6, she enjoyed meeting people and the pure joy of competition. But as Tran continued her ascent in the sport, she lost friends because of their behavior on the court.

"I mean, everybody calls balls out that are in at some time. No one is perfect. Even if you think it's out and it's in, I wouldn't consider that cheating," said Tran, the No. 1-ranked junior in the Mid-Atlantic girls' 18-and-under division. "But when people blatantly cheat, like repeatedly, over and over and over again, it's kind of like, 'I don't want to associate with this person.' There's clearly something underneath that. That's not something I want to be around."

Tran added that dealing with cheating is an unavoidable part of competing in junior tennis.

"Everyone has their war story of cheating," she said.

During a match, players can call for an official to observe, or plead their case, but the official probably will not stay for the entire match and players must stop play if they want to replay the point, USTA director of junior competition Lew Brewer said.

While Brewer added that "bad calls are just part of the game," the USTA compiles a centralized database of violations, including grievances filed for cheating , which can lead to suspensions. And in recent years, the USTA has introduced a player pledge and a national leadership award to encourage good sportsmanship.

Bethesda-Chevy Chase junior Zoe Howard wrote a first-person essay for Sports Illustrated in March about the cheating she has witnessed in youth tennis and said that in some countries "neutral parents, spectators, third party volunteers, or even other players" can monitor matches.

PlaySight, an Israel-based sports technology company, recently introduced a video replay system for junior and collegiate tennis in efforts to "curb cheating." The Virginia Tech men's tennis team was the first to test the technology, and it has been used at USTA-sanctioned and college tournaments. But it comes with a hefty price tag. Six of the Hokies' 18 courts have been outfitted with the highest-level technology the company offers, which costs about $30,000 per court.

It is also possible that perceptions of cheating do not match reality. During a match at Battle in the Burg, a prestigious tournament held in Fredericksburg, Va., play was occasionally halted after contentious points between two highly ranked girls in the Mid-Atlantic.

Parents of the players afterward were adamant that their daughter's opponent, and not their daughter, was the one making poor line calls — a phenomenon that University of Pennsylvania professor Maurice Schweitzer defines as "motivated beliefs," or as some in the sport call it: "parent eyes."

"What we want to believe is different than what we must believe," Schweitzer said. "I see the line call as clearly in. You see it as clearly out. In reality it was a close call, but we're interpreting the same data very differently."

For some players, the cognitive dissonance between players (or their parents) is far more common than intentional, blatant cheating.

"If I felt I had a bad line call on the other side, I wouldn't think it was on purpose or the guy was trying to do it intentionally," said 24-year-old Jack Sock, one of the top American men on the pro tour. "We're kids, and out there, maybe we can't see the best sometimes. . . . I didn't see [cheating] was a huge problem at all."

Even if some players aren't intentionally making bad calls, the system makes it easy for those tempted to cheat, according to Schweitzer, who co-wrote the book "Friend and Foe: When to Cooperate, When to Compete, and How to Succeed at Both."

"You have almost all of the ingredients possible in junior tennis to promote cheating," he said. "You have pressure from your parents and peers, you have other people who are systematically doing it. . . . The line calls themselves are quite fuzzy and difficult to detect."

Ultimately, because of the way junior tennis is structured, the integrity of the sport often comes down to the players on the court.

When tournament officials at the 2009 Easter Bowl tournament in California called Liang to the front desk, she initially thought she was in trouble. So did her mother.

But officials summoned Liang not to admonish the young player but to honor her with the tournament's sportsmanship award. It helped that during one crucial point late in the tournament, Liang said, she called her opponent's ball out but then overturned it when she realized the ball might have clipped the line. This was the first of many sportsmanship awards Liang would win both nationally and at the Mid-Atlantic level, and the plaques are proudly displayed in her childhood home in Potomac.

"I just try to be conscious: It's really just a sport, and it's a game, and you should be having fun when you're playing," Liang said. "You shouldn't feel so much pressure to make bad line calls."