COLUMBIA, Mo. -

A Tipton High School football player remains in the hospital after suffering an injury last week. For days, Chad Stover has remained in critical condition at University Hospital in Columbia.

School officials say he suffered a severe brain injury during the game. While details on his exact injury are still unclear, attention has been put on head injuries on a national level.

Recently, the National Football League agreed to pay $765 million to retired players who sued the league over head injuries.

But medical experts say the risk starts at a much younger age, with teenagers whose brains are still developing.

ABC 17's Kristie Reeter analyzed what plans high schools have in place to deal with concussions in all sports and what parents should know about the injuries.

According to data released by the Missouri State High School Activities Association (MSHSAA), there were more than 2,500 students held out of practices and games statewide because of a concussion last year.

Football, wrestling and girls basketball were the top three sports in Missouri for reported head injuries.

Because of those head injuries, athletes missed more than 3,000 days in the classroom. Even worse, those injury reports more than doubled from the previous year.

For some Missouri students, athletic scholarships may be their only chance at college and perhaps a career in sports. However, an injury during the game could prove to be a game changer in life.

Jackson Nicoli, a Hickman High School senior, suffered three concussions in the span of 18 months.

His first concussion was during a football game, followed by one in a gym class then a third during football practice.

"I have headaches, I forget things that usually most people wouldn't forget," Nicoli told Reeter.

After visiting a specialist, Nicoli decided to quit football because the risk was too great.

Concussions are caused by a direct or indirect jolt that shakes the brain inside the skull.

"In severe enough instances, it can actually hit the side of the skull and causing the injury to the brain," said Pat Forbis, the coordinator of sports medicine at St. Mary's Health Center.

He says people need to rest the idea that if you have a concussion, you have to be knocked out. Forbis says sometimes athletes can look normal after a concussion, then two-to-three hours later start showing symptoms like dizziness, headaches and sensitivity to light.

If a concussion is not caught, dire consequences can happen.

"There is a thing called the second impact syndrome," said Forbis. "What happens is the brain begins to swell. Fifty percent of those who have this injury are pretty well incapacitated mentally the rest of their life. The other 50 percent die."

He says it's suspected this happens in athletes up to the age of 19 who keep playing before a concussion has healed.

Even with the potential outcome, it has only been in the last several years that major changes to concussion protocol have happened.

In 2011, a law passed in Missouri, which requires a youth athlete suspected of having a brain injury to be removed from competition for at least 24 hours. To come back, the athlete has to be cleared by a health care provided trained in concussions.

MSHSAA helped write that law and also has additional guidelines on top of it for returning athletes to play.

"We have a protocol in place that goes over about a seven-day period of time," said MSHSAA associate executive director Harvey Richards.

Those steps included rest and light exercise. Once symptoms of a concussion are gone, the athlete can progress back into play, which could be days or weeks.

"For kids, 12 to 13 days was the earliest they got back into play," said Forbis. "Then we have some that are 100, 200 days.