Both of his parents are deployed overseas in the military - his mom in Iraq, his dad in Korea. Marcus' parents are divorced, and while his mom is away he has been living with his stepfather in Augusta, helping out with extra chores such as washing dishes, caring for the dog and helping his half-brother with his studies.

"It's kind of depressing," he said recently, reflecting on how as a senior at Academy of Richmond County he has achieved certain milestones that his parents have been unable to enjoy with him. "It really takes a toll on me."

So does, Marcus added, having to move six times because of military reassignments.

"Friends it was always hard to make because you were only there for a little time," he said, adding that he has also had problems with records transfers, sometimes losing credit for classes.

Marcus is among the thousands of children who must cope with the sacrifices that come from having a parent in the military. And amid prolonged wars in Iraq and Afghanistan, a new study suggests deployments are having an effect on military children.

"Our nation did not anticipate such protracted conflicts. We owe it to military families to better understand and address the challenges they are facing today, and may face tomorrow," said Mary Scott, the head of the board of governors of the National Military Family Association, in a recent news release.

Ms. Scott's organization recently commissioned a study into the challenges military children face. The study was conducted by the Rand Corp. and released earlier this month.

It found that children with a parent in the military are more likely to experience emotional difficulties or issues in the classroom when their parent is deployed.

"Our findings suggest that the more time parents are away, the more likely it is that children will experience problems," said Sandraluz Lara-Cinisomo, a co-author of the Rand study, in a news release.

The study examined 1,500 military children throughout the country and found that older children from military families had more problems in school, yet girls had fewer issues in class and with making friends than boys did. However, girls had a higher level of anxiety than boys.

The study found that more services might be needed for the families of those deployed.

Richmond County school system spokesman Louis Svehla said the district compiles what are called "federal cards" annually for each military student. The school system's count this year isn't expected to be complete until after the holidays. Before this year, the number of students who have a parent in the military and live off base, attending a Richmond County school, has varied from 4,806 in 2006-07 to 4,576 in 2007-08 and 4,578 in 2008-09. That's about 14 percent of the system's overall 32,500 student base.

Academy of Richmond County has one of the county's highest concentrations of military students because all high school-age students living on Fort Gordon must go there.

Those living on base and in kindergarten through eighth grade attend Freedom Park School, which in October had an enrollment of 808.

As for Columbia County, officials say they are still compiling the military student total this year. Last school year, the system had 1,909 students with parents in the military, accounting for 8.6 percent of the system's overall 22,055 student population.

Nationwide, the Military Child Education Coalition states there are more than 660,000 U.S. school-age children who have a parent serving on active duty. There also are about 500,000 children with a parent either in the National Guard or Reserves, 72 percent of which are school-age, according to the coalition.

Marcus said that of all the schools he has attended - including those in Germany, Alabama, Virginia and other parts of Georgia - he has felt most at home at ARC, and he said his mom has assured him he'll be able to graduate there.

"I was tired of moving ... so I decided to stay here," he said. "This is one of the places I can actually remember having friends."

Marcus said he has experienced many challenges through the years with moves and his parents' deployments. For one, he said, he has often been unable to be on a school's football or track team - his two favorite sports - because of moves during the season.

And a common theme is the issue of making friends.

"One of the hardest things is leaving my friends, and most of them are my best friends," said Grovetown Middle seventh-grader Frankie Brown, whose mom, Lt. Col. Muriel Brown, is active duty in the Army and based at Fort Gordon.

"You get to see them for about two years, and then you have to move, and then you won't ever see them again," Frankie said.

Lt. Col. Brown said they've had about five moves since Frankie was born, and each time she tries to do research ahead of a move to show her son that the activities he's involved in can continue at their new hometown "so he can start thinking ahead that not all is lost."

Lt. Col. Brown said she has had no transfer or other class issues as a result of frequent moves, noting that each school she has dealt with has been helpful. She also said the military offers support groups.

"It helps the family to stay bonded and to know not just one family is in this situation," she said.

Army Sgt. 1st Class Tremayne Webber, who is based at Fort Gordon and has four boys age 2, 8, 11 and 16, said he has also noticed how moves and deployments can take their toll. He said his family generally moves about every three years and "it's like they start over from scratch," noting that curriculums also were "totally different" when they moved here from Arizona earlier this year.

His 11-year-old son, Trevion Webber, who is in the fifth grade at Freedom Park, said he found it harder to focus on studies when his father was in Iraq last year.

"The hardest part for me is trying to do my school work and not thinking about my dad when he's deployed," he said.

Imani Jenkins, a freshman at John S. Davidson Fine Arts Magnet School whose dad retired from the military in October, moved to Augusta from New Jersey in 2006. Before that there were stints in Beaufort, S.C.; Tennessee; North Carolina; Italy; and Germany.

She said she also knows about taking over extra house chores - from walking the dog to keeping a check on her own grades. She did so when her father was deployed to Iraq a few years ago. These days, Imani is staying put in Augusta and believes coping with moves and deployments made her a better person and student, teaching her to "grow."

But she agreed that "leaving behind friends was the hard part."

Marcus said technology has helped him keep in touch with his parents while they've been deployed. "I can call her on her cell phone," he said, noting how his mom and dad have phones they can be reached on at any time.

An in-person visit, though, he admits, is hard to beat. He said he last saw his mom in August when she came home from Iraq during a two-week leave. He said she's set to come back again in February.

And while sitting in a room at his school as his principal popped in to point out how he's a good student and kid, Marcus smiled. Thinking of his mom, he quickly added: "She's missing a lot."