WASHINGTON — Doctors warned lawmakers today that student athletes risk altered lives and permanent brain damage if schools don't protect them from the effects of blows to the head.

A House committee grappling with how to safeguard young athletes also heard from an NFL player who recently retired because of post-concussion problems; a mother whose son, a University of Pennsylvania football player with brain damage, committed suicide; and a high school girl unable to keep up with her classes since suffering a concussion on the soccer field.

Education and Labor Committee Chairman George Miller, D-Calif., cited estimates of 300,000 sports-related concussions a year. The actual number, if recreational and playground injuries are included, is far higher, he said.

Miller has introduced legislation that would require school districts to develop plans for concussion safety and management and increase student and parent awareness of their dangers. Schools also would have to provide support for students recovering from concussions.

Students suspected of sustaining a concussion during a school event would be prohibited from returning to play that day and require evaluation by a health care professional.

Several states have adopted similar measures, but Dr. Gerard Gioia, chief of pediatric neuropsychology at Children's National Medical Center in Washington, D.C., said standard guidelines are crucial.