Dec. 4, 2009 -- Niki Popyer was in seventh grade when she hit her head on the gym floor and had her first concussion. Her freshman year of high school, she got fouled during a basketball game and endured concussion No. 5. That time, she couldn't see for a while afterward.
By age 16, the New Jersey girl had had 11 concussions, some just days apart. The repeated trauma to her brain took its toll on her once-normal life.
"Taking notes [in class is] impossible," Popyer told "Good Morning America." "I can't finish tests. I get through maybe half of it. Then, when I get home, if I make it the whole day at school, I come home and I sleep or I just, like, sit on the couch. ... It went from, like, my future's going to be basketball to I hope I can get into college."
Popyer is just one of hundreds of young girls who are paying a hefty price from sports injuries. A recent study in the American Journal of Sports Medicine reported that athletes who had recent concussions generally showed poorer than average thinking skills and reaction times. According to the study, this was especially true in young women.
Another study found that female high school soccer players are 68 percent more likely to get a head injury than their male counterparts and, in basketball, three times more likely than males.
Experts say the disparity could be due to a weakness in skeletal structure or a surge of hormones leaving them vulnerable to injury. The biggest problem, they say, is repeated blows to the head before the injured brain has healed.
"It's really important to ensure that somebody does not have active symptoms before we return them to any sort of physical exertion or even mental exertion in a big way," Popyer's neuropsychologist, Dr. Jill Brooks said.
Though her father was her basketball coach, Popyer's parents worried that their daughter should stop playing, but doctors kept clearing her and didn't take the concussions seriously, they said. No one seemed clear on how long she should rest.
National Guidelines for Head Injuries
"On some occasions we were summarily dismissed as hysterical parents," the girl's mother, Cathy Popyer, said. "You know, 'She just got hit in the head, everything's fine. Don't worry about it.'"
According to Brooks, the Popyers were never given a "full picture" of how to manage their daughter's injuries and were not told how long to wait before allowing her to return to activity.
In most states there are no uniform guidelines about how long young athletes should be required to sit out after a head injury. New Jersey Rep. Bill Pascrell, a leading advocate for improved treatment of traumatic brain injuries in U.S. soldiers, said he is trying to change that.
"[It's the] same as the Army, as not screening soldiers before putting them back," Pascrell said. "There's no blood, there's no contusion, and yet that individual could be severely damaged for life. Now we're going to send them back out there."
The Democrat is pushing a bill to raise awareness about concussions in student athletes. He said he wants to establish firm national guidelines on when brain injured students should return to play, if at all. The bill is being co-sponsored by Sen. Robert Menendez, D-N.J.
"That young lady, what in God's name did we put her through?" Pascrell said, referring to Popyer. "And to look back at it, don't tell me couldn't have done anything about it. I don't believe it."
After suffering so many injuries, Popyer is grappling with an uncertain future and a college career that has been sidelined.
"I always wanted to, like, go to a good school for basketball," Popyer said. "So that's been pretty upsetting."
Popyer still gets calls from colleges interested in her playing basketball for them. She said she has to turn them down.