When Joe Kirby Jr., a point guard for Sagemont Upper School in Weston, collided with two players during a game in February then fell backward, slamming his head on the basketball court, the 10th grader didn’t know what hit him.

“I was really dizzy. But I was in denial when I heard the word ‘concussion.’ I just wanted to get back in the game,’’ he said.

It used to be that youth athletes would “get clocked’’ with a hard hit to the head during a play, then shake it off and get back to play. Winning came first.

But those days are over in Florida.

A new state law, signed by Gov. Rick Scott in March and which went into effect on July 1, aims to put kids before the game. It requires concussion training for coaches, officials and athletes before the start of every playing season and the complete recovery documented by a physician before injured athletes are allowed back into play.

“Concussion is common but can have serious long-term effects, especially for young athletes who do not get proper rest to heal and rehabilitate,’’ said Dr. Dan Grobman, a sports medicine specialist at Cleveland Clinic Hospital in Weston.

Parents and students are also now required to sign a consent and release for liability agreeing to report injuries of their own or of teammates.

Grobman said young, still developing brains are more prone to permanent cognitive damage, especially when the concussion goes unreported and hence untreated.

Secondary and additional concussions compound the injury and can cause severe symptoms including mood swings, depression, suicidal tendencies, debilitating tremors, and chronic traumatic encephalopathy (CTE), which is commonly known as “punch drunk syndrome.’’ Death is not out of the question.

After all, concussion is a traumatic brain injury (TBI) when the head or body takes a blow forceful enough to snap or twist the brain against the skull, causing brain cell damage and chemical changes that could last a lifetime.

“The law addresses a national epidemic. We are at the tipping point,’’ said Dr. Gillian Hotz, director of the concussion program at UHealth Sports Medicine at the University of Miami and chair of the statewide Concussion Task Force that pushed the Florida law forward.

The Centers for Disease Control and Prevention reported in October 2011 that youth sports-related concussions had surged nationwide by 60 percent from 2001 to 2009 to an estimated 173,000 non-fatal injuries per year.

TBI among boys happens mostly in football; girls are likely to suffer TBI playing basketball or soccer. All contact sports, including wrestling, lacrosse and cheerleading, pose a threat of head injury.

Florida is the 34th state to adopt concussion laws for youth athletes.

“For so many years people didn’t think of concussion as a major injury. It has been only recent since professional football players started filing lawsuits against the NFL that people started to think differently,’’ said Jeff Mangus, the head trainer for Sagemont Upper School.

More than 3,000 former professional football players have sued the National Football League for diminished body and brain functions they say are due to untreated or repeated concussions.

Damian Huttenhoff, director of Athletics and Student Activities for Broward County public schools, said the recent suicides of concussion-plagued NFL alumni Dave Duerson (in 2011), Ray Easterling (in 2012) and Junior Seau (in 2012) put sports-related TBI in the headlines. The heartbreaking story of Cypress Bay High School linebacker Daniel Brett, who took his own life last year at age 16 after a series of concussions led to multiple disabilities, drove the problem home.