Several of the area's best volleyball players in Loudoun and Fauquier counties have been getting a thumbs-up from their coaches on the team bench this season. The sign hasn't been delivered as an affirmation -- as it is most commonly associated -- but as a direction.

A thumbs-up in volleyball means one thing: jump serve. It's a technique high school teams are using with more frequency, and it's something spectators can plan to see plenty of when the AA Dulles District semifinals and AA Northwestern District final are played today.

"Jump-serving is where the game is going," Fauquier Coach Diana Story said. "The girls see that from watching college and national-level play, and they want to be a part of it."

A year ago, for example, only a couple of players in the Dulles and Northwestern districts dared to jump-serve in live competition. This season, more than a dozen players have done so.

Fauquier senior Kathleen Crosby (84 percent of her 228 serves have been on target this season, with 62 aces) and Potomac Falls senior Emily Mims (84 percent of 282 serves on target, with 85 aces) are at the forefront of the movement. They are the only two area players who don't need a sign from their coach before jumping, but instead have the green light to do so every time. That, Story and Panthers Coach Linda Lachey-Helms agreed, is a first for their programs.

"I've never had a player who jump-served 100 percent of the time," Story said. "But Kathleen is very consistent and not afraid at all to do it. And that's the perfect combination. You have to have tremendous confidence to be successful with that kind of serve."

In a victory over second-place Sherando late in the Falcons' run to the Northwestern District regular season title, Crosby had struggled with her signature serve and was visibly frustrated by multiple attempts that sailed beyond the end line. But with her team up 2-1 in games and leading 20-16 in the fourth, an undeterred Crosby registered back-to-back aces with her jump serve and added three more points to seal the victory.

"I'm not sure when it happened, maybe our second game this year, but it just really started to click for me," Crosby said. "And I knew then I was comfortable enough, and confident enough, to keep doing it."

Stone Bridge junior Samantha Ingersoll and senior Emily Vera also have jumped on the majority of their serves this season, but both first must get the okay sign from Coach Jill Raschiatore. Raschiatore said she sometimes will keep them grounded if she feels they're out of sync or if the game is at a particularly critical juncture.

"We're always going to play to win, and so we try to be aggressive," Raschiatore said. "But if it's a situation where it's more important we get the ball in play, then we don't usually have them do it. I guess it really depends on how they're doing at the moment. If one of them just killed the ball out there and everyone is fired up, that's when we like to have them do it."

Vera said that since she has become more comfortable with all the elements of a jump serve, she would prefer to do it every attempt.

"It takes a while to learn because you have to make sure your toss is exactly the same every time," Vera said. "It has to always be a certain distance in front of you and a certain height. It's just repetition, and learning to read your toss so that if it is off you can adjust your approach. But I'd rather jump-serve than stand on any given day because it's just a much harder serve. And if you can get a nice, topspinning jump serve in, then the other team is less likely to be able to attack."

Loudoun Valley junior Blair Brown jump-serves less frequently than Ingersoll and Vera, but she and teammates Allison Hamilton, Amanda Kole and Sarah Neikirk all have done it during matches.

"I really like doing it, but you have to really be consistent at it, and to do so, you have to do it a lot," Brown said. "We practice it a lot, so that helps. But when you get on the court, you're still kind of nervous because it's just not as consistent as a normal serve would be. There are so many things that can go wrong with your toss or timing or jump."

For that reason, Vikings Coach Laird Johnson said his jump-serve calls are entirely situation-based.

"If I see a rotation in there that we want to take advantage of, I'll have them do it," Johnson said. "In most situations this year, we've had Blair do it to close games, which is maybe a bit unusual. We won't have her go up if it's 24-23, but we will if it's 24-18. And as she gets better at it, we'll go to it more.

"We do work on it every day in practice. My goal is to have every girl on the team be able to jump-serve by the end of the season, whether it's in a game or not."

Story said her entire team practices jump-serving in practice as well, but most players are too inconsistent -- and therefore afraid -- to try it in a game.

Potomac Falls senior Lindsey Facemire, one of the few who jump- served frequently last season, has done so this year with far less frequency because of similar nerves. But Panthers sophomores Lauren Fauteux and Clara Flanagan have also dabbled sparingly with jump serves during games, and Lachey-Helms hopes that will increase over time.

"I'm actually trying to encourage our girls to do it more," Lachey-Helms said. "Like with Lindsey, I'd rather see her go up than stay on the floor every time, but I also want her to feel comfortable.

"The fact is, though, that in high school it can be a real big advantage to jump. Because sometimes, even if the serve isn't quite as good, the other team just sees someone jump-serving, and they get scared. Now, that's less effective against the teams whose teammates do it, because they're used to seeing it in practice. But anytime you can give opponents a look at a variety of serves in a match, you've got an advantage. That's why you're seeing it so much more."

Fauquier senior Kathleen Crosby uses a jump serve.Fauquier's Kathleen Crosby has been successful on 84 percent of her serves.