(CNN) A high school football player in Illinois has died after suffering injuries during a game.

Andre Smith, 17, died of "blunt force head injuries due to a football accident," according to the Cook County Medical Examiner's Office.

He hit his head on the final play of the game, walked off the field but later collapsed, the affiliate said.

Smith was a senior at Bogan High School.

According to the Illinois High School Association, Smith was the seventh high school football player to die this year nationwide.

"As anyone who has participated in athletics knows, there is a risk of injury any time a player steps on the field of play. Football, in particular, has been under the microscope over the last decade, and organizations at all levels of play, including high school, have been taking aggressive steps to try and reduce injury over time," the group said in a statement

Survey: 11 deaths last year related to HS football

The number of young athletes whose deaths are related to high school football fluctuates from year to year.

In 2014, five high school players died of causes directly related to the sport, such as head and spine injuries, according to a survey by the National Center for Catastrophic Sports Injury Research at the University of North Carolina.

Another six players died of indirect causes: Three were heart-related, one died from heat stroke and two were caused by hypernatremia (an electrolyte imbalance) and water intoxication, the survey found.

The past decade has seen an average of three fatalities each year directly attributable to high school football, the survey said.

In 2013, there were eight deaths directly linked to high school football.

Between 2005 and 2014, the deaths of 92 other high school football players were indirectly related to the sport, according to NCCSIR.

Why death rates are higher at high school level

The reason for the high number of high school football fatalities compared with college and professional football has to do with numbers.

There are about 1.1 million high school football players in the nation, compared with about 100,000 in the NFL, college, junior college, Arena Football and semiprofessional level, the NCCSIR survey found.

High school football players suffer three times as many catastrophic injuries -- deaths, permanent disability, neck fractures and head injuries -- as college players, according to a 2007 study in the American Journal of Sports Medicine.

Kevin Guskiewicz, co-director of the Matthew Gfeller Sport-Related Traumatic Brain Injury Research Center at the University of North Carolina, said the developing brains of high school athletes are more vulnerable to catastrophic head injuries.

In addition, the skill level of many younger athletes leaves them more susceptible to serious injuries.

Making matters worse, nearly 70% of high school athletes with concussions played despite their symptoms, and 40% reported that their coaches didn't know of the injury, according to a 2014 study in the American Journal of Sports Medicine.

Study: More full-time trainers needed

The risk of serious injuries and death at the high school level is exacerbated by the shortage of full-time athletic trainers at practice and games -- due largely to costs.

A study this year in the Journal of Athletic Training said only 37% of the nation's public high schools have full-time athletic trainers.

"Nearly all of the causes of death in sport are influenced by the care in the first five to seven minutes," said one of the study's authors, Douglas Casa, a professor of kinesiology at the University of Connecticut.