Lindsay Sullivan, the optimist, dreams of making the stoic Buckingham Palace guards crack a smile during a school trip to England and Ireland.

Lindsay, the realist, thinks of something more sobering: When will the world feel safe enough for her school district to allow the 10-day trip to take place?

The junior at Howard County's Atholton High School has learned the hard way that uncertainty is a given in an age of terror alerts and global strife. Last week, Howard school officials ended months of hand-wringing by calling off her trip and all other travel abroad through June, saying the risks for students are too unpredictable as war with Iraq looms.

A year ago, she lost out on a similar trip, canceled after the Sept. 11, 2001, terrorist attacks.

"It's just so disappointing and upsetting," said Lindsay, who holds out hope that this year's trip can be rescheduled for summer. "I feel sort of helpless because I can't really do anything about it."

In the weeks and months immediately after 9/11, overseas school trips and student exchange programs were curtailed without much room for doubt. Now, however, students and their parents are often kept guessing -- in some instances, until the day before the scheduled departure.

And with wartime restrictions on travel insurance, the possible cost to kids is about more than missing the most exciting journey of their young lifetimes. "That is a lot of money," said Lindsay, 16, who has been socking away cash from her part-time job at a pizza parlor to help pay for her $1,900 trip. "To me, I make like $40 a week in tips, so that's like two years' worth of money."

The student-trip segment of the nation's travel industry, which increased as much as 25 percent every year in the 1990s, did not grow at all last year, a result of both post-Sept. 11 travel jitters and the slumping economy, said Michael Palmer, executive director of the Student and Youth Travel Association. The group represents 360 travel agencies, hotels and restaurants catering to schools.

At the start of this school year, educators showed a renewed enthusiasm. Teachers planned excursions to France, Germany, China and many other countries, leading Palmer's association to project that student travel would grow 15 to 20 percent.

Casey Holmes, an eighth-grader at Eastern Middle School in Silver Spring, was one of the students who took advantage of the opportunity. She signed up for an 11-day French Educational Exchange Program, which allowed her to stay with a French family for six days, then tour France for five days. Casey, 13, returned from the trip Monday, singing the praises of her overseas journey. "We got to experience the culture, the traditions and the country of France, and that's something that you can't get in a classroom," she said.

Other students have not been as fortunate. Yesterday, in fact, the superintendent of Casey's school district canceled all international travel for students and staff.

In the fall, 14-year-old Austin Alderman signed up for a trip to Quebec with his French class at Crofton Middle School in Anne Arundel County. In the months that followed, Austin mowed lawns, shoveled snow and resisted buying the latest "Sum 41" CD to earn and save spending money for the five-day trip in May. Two weeks ago, he started thinking about what to pack and who his roommates should be.

Then his teacher told the class that the trip was canceled, with each student's $100 deposit lost. Two days later, Austin was told the trip was back on -- though it could be called off at any moment. He went from crushed, to relieved, to skeptical.

"I definitely think they're going to change their mind again," he said. "But hopefully they'll change it back again and we'll still be able to go."

The apprehension comes from overseas as well. School groups in Japan, for example, called off student exchange programs with U.S. schools in recent months, citing safety concerns, said Jeff Hild, assistant director of the Council of International Educational Exchange.

And as many as three French students expected to visit Eastern Middle School later this month during the second half of the French exchange program decided not to participate, citing safety concerns, said Moreno Carrasco, the school's principal. Carrasco, who accompanied his student group to France, said he was asked to address French parents to help calm their fears about letting their children visit the Washington area.

"Many of the parents, after my speech, thanked me for helping them think that their kids would be fine in America," Carrasco said.

For many local schools, uncertainty carries a big price tag. McLean High School in Fairfax County has a $2,450-per-student trip to China planned for 72 band members. It stemmed from a prestigious invitation from the Chinese Ministry of Tourism, and students worked hard to raise money to cover their travel costs, said James Kirchenbauer, the band director.

Cancellation insurance was built into the trip price, but the policy does not offer refunds in war situations. Kirchenbauer said the agency he is working with has assured him that students should get their money back based on the long-standing relationships the company has with tour operators. But he still watches the latest world news accounts anxiously, a bomb in the Philippines suddenly much more relevant.

"I'd hate to see us lose the opportunity," Kirchenbauer said.

Kenneth P. Lawson, associate superintendent for instruction in Anne Arundel, said he appreciates how difficult the back-and-forth must be for students and chaperons. Still, he can't imagine any alternative. School officials are trying to balance the benefits of travel against the risks for students -- and at a time like this, drawing the line isn't easy, Lawson said.

"The circumstances that we're all trying to familiarize ourselves with and feel comfortable with are different from anything we've ever had to deal with before," Lawson said.

McLean High band director James Kirchenbauer rehearses students for a trip to China. "I'd hate to see us lose the opportunity," he said. Flutists Marie Chinworth, left, Stephanie Stevens, Raedun Knutsen and Tarin Ain are among the 72 McLean band members who hope to make the trip at a cost of $2,450 each.Atholton High junior Lindsay Sullivan marked down the days last week until a class trip to England and Ireland. Not long afterward, the trip was canceled.