The Loudoun Valley football team is seen before its scheduled practice on Thursday in Purcellville. (Richard A. Lipski/For the Washington Post)

Amid widespread debate about head trauma and the safety of playing football, parents of the athletes at Loudoun Valley High School in Purcellville, Va., were thrilled when a Bethesda, Md., company offered to place impact sensors on team helmets. A light would turn on when a helmet took a big hit, an indicator that trainers should check for a concussion.

Brain Sentry, partnering with Inova Neuroscience Research, wanted to put the sensors on all Loudoun football and lacrosse helmets to identify the risks athletes face and to study data from more than 2,000 students.

But Loudoun County school officials declined the offer, saying that the sensors lacked sufficient testing and that the one-ounce devices could void the helmets’ safety certification. They also said they worry that the sensors could report false positives, that the school system doesn’t have enough trainers to properly monitor players wearing the sensors and that opponents might target key players if they know that tripping a sensor could mean getting someone off the field.

While both sides say students’ safety is their priority, the school system’s decision set off a battle with the group of Loudoun Valley parents, who almost immediately defied school system orders forbidding the sensors. On Thursday morning, with school administrators present, about 30 players walked across the high school’s practice field to the parents group, watched the parents place the sensors on the back of the helmets, and then began to practice.

Also watching was a group from Brain Sentry, including former Washington Redskin Charles Mann, a company board member. With the tension building, Mann told about two dozen parents: “We’re gonna laugh five years from now when these are a part of life.”

A detailed picture of four sensors, know as Impact Counter Plus. Parents are defying their county school administration by placing the sensors on the back of football helmets of Loudoun Valley players who voluntarily choose to have them. (Richard A. Lipski/For the Washington Post)

The team of about 95, including junior varsity players and some freshmen, practiced without helmets for about two hours. About 10 a.m., the helmets went on and drills resumed.

Assistant Principal William Oblas watched for about 15 minutes before walking onto the field and stopping practice. Gathering the coaches around him, he told them that no player with a sensor on his helmet would be allowed to continue practicing.

So the coaches told all the players to remove their helmets.

The remaining parents, mainly the leaders of the school’s football booster club, did not want to put head coach Danny McGrath and his staff in the middle of their year-long struggle with Loudoun administrators. So they went onto the field and stripped 24 sensors off the helmets, about three hours after they went on.

“Now we go to the school board,” said Dee Howard, who helped lead the parents group and raised money through the booster club to purchase the sensors. “Now we go to the other sports.”

School district spokesman Wayde Byard said the parents didn’t have to remove the sensors.

“We did let the coaching staff know that anybody with a sensor could not practice,” Byard said. “They could do non-contact drills. But if they wanted to practice with their helmets on, they had to have the sensors off.”

Debbi Alexander, a parent, presses a sensor onto the back of the helmet of Loudoun Valley football player Philip Akin, 16, as his mother, Terry Akin, watches in Purcellville. (Richard A. Lipski/For the Washington Post)

Such sensors are at the center of discussions about concussions and head injuries in football, from peewee leagues to the NFL. With increased attention to football head injuries and their long-term effects — and some NFL players donating their brains to scientists who are studying the issue — some argue that the sensors are a way to start collecting data that could save lives.

Brain Sentry’s sensors are on helmets in the Arena Football League, NCAA powerhouses Louisiana State University and the University of Alabama are using them in practice, and youth leagues in Rockville, Georgia and elsewhere are also using them on the field. Mann said he recently watched an arena game in which one sensor alerted, the player was checked and the player returned to action.

The sensors have not been certified by the National Operating Committee on Standards for Athletic Equipment, which sets the impact standards for football helmets. But Greg Merril, the founder of Brain Sentry, said the sensor had been tested “on a variety of helmets by [the committee’s] technical director, David Halstead, and the results showed that the sensor had no adverse effect on helmet performance.”

Mike Oliver, the committee’s executive director, said that as a parent, he would want to know what the false-positive and false-negative rate is for the sensor’s alert. He said some hits that might not register as particularly hard, such as a quarterback falling and hitting his head on the turf, can cause serious damage, while some hits that register as high-acceleration could cause no damage.

“I’m not saying don’t use them,” Oliver said. “But you need to understand what it does and doesn’t do.”

James Ecklund, director of the Inova Neuroscience Institute, said there is a need for better diagnostic tools for concussions.

“Right now, it boils down to judgment and patient self-reporting,” Ecklund said, adding that if Loudoun had wanted to use the sensors, “we’d be happy to help design a project that could track the numbers and the data and determine if it’s a helpful device or not.”

Merril’s offer to outfit Loudoun Valley’s team came after The Washington Post reported last year that team parents and assistant coaches questioned whether playing larger schools might expose their players to more head trauma. Brain Sentry provided liability insurance of $6 million and offered 120 free sensors.

Loudoun schools officials declined.

“We don’t feel that participating in being an instrument for validating a device that’s going to be marketed is a primary objective for us,” Deputy Superintendent Ned Waterhouse said in an interview. “Our primary objective is safety. We don’t feel that this necessarily is a proven strategy for student safety.”

Howard, whose son plays for Loudoun Valley, said she doesn’t understand why the school system wouldn’t want to be at the forefront of safety enhancement in high school football. Pam Cordani, president of the football booster club, feels the same way.

“Anything to reduce the risk of concussions is a positive,” Cordani said. “I look at it as nothing more than a pedometer, another tool in our toolbox.”

In February, Brain Sentry teamed with Inova Neuroscience Research to offer a proposal for monitoring football and lacrosse head impacts, declaring that “underreporting of concussions is a problem” and that Brain Sentry’s sensors would be “used to augment the usual means of identifying which players need to be assessed for concussion.”

“Loudoun County will be at the forefront of advocating for player safety,” the proposal stated, “as the first county in the nation to mandate sensors on football and lacrosse helmets for the entire county.”

The 3-by-1-inch sensors attach with peel-and-stick tape. They measure linear acceleration, or a sudden back-and-forth jolt, rather than a rotational movement. The sensors activate a light signal when that acceleration exceeds 80g of force. The sensors don’t indicate that a concussion has occurred — no technology can do that — merely that the helmet has taken a hard hit.

Brain Sentry has added a counter to the device, which keeps track of how many hits the helmet has absorbed. Some think the number of hits a player absorbs can be just as important as the hardest hits.

Loudoun Valley parents said school officials declined to meet with the booster club to explain their concerns with the devices, but on Wednesday night, Loudoun Valley Principal Susan Ross sent out a detailed letter about the sensors.

“There is no scientific proof that helmet sensors are effective and no nationally recognized medical protocol for their use,” Ross wrote. She said the county has a “well-articulated concussion protocol” and that medical professionals have “a concern with false negatives and false positives with the sensor,” among other issues.

“In sum,” Ross wrote, “the combined unknowns constitute a risk that we are unwilling to take.”

Byard said the county — which has struggled to fully fund the school system amid budget cuts — does not have the resources to conduct testing on 2,000 football and lacrosse players. He said that “the best sensor is a human being who knows the athletes, who regularly monitors practices and regularly monitors games. They are trained to monitor and assess injuries.”

Waterhouse said the sensor issue puts the school system in a difficult position because school officials care deeply about student safety but don’t want to be field-testing a product.

“We’re being told we’re not interested in safety if we’re not willing to be the alpha set for this test validation,” Waterhouse said. “And I don’t think that’s fair.”