The reports from middle and high schools across Massachusetts, collected under a state law passed in 2010, highlight the extent of the problem at a time when medical experts and sports leagues, from Pop Warner to the NFL, are increasingly worried about the long-term effects of head injuries.

Boston College High School, an all-boys private school in Dorchester with grades 7 through 12, reported the highest number, with 76 head injuries sustained last school year during “extracurricular athletic activities,’’ according to reports released to the Globe by the state Department of Public Health under a public records request. Lexington High School followed with 69 reported head injuries or concussions.

“I think kids now are more aware and recognize the dangers of head trauma,” said Jon Bartlett, athletic director at BC High, which has about 750 students playing 17 sports. “You’re seeing bigger, faster, stronger kids these days, so the collisions are a little more violent than years ago.”

But the reports also show a wide variance in the number of head injuries reported at Massachusetts schools, either as a result of differing reporting standards at schools or confusion over the new law. About 525 schools, including some private institutions, missed the August reporting deadline. There is no penalty for not reporting on time.

Twenty-nine schools reported head injuries in the single digits, a sharp contrast to the dozens reported by other schools. While several of the schools with relatively few head injuries are charter schools or private schools with limited sports offerings, low numbers were also reported by large sports programs.

Medford High School, New Bedford High School, and Newton North High School have significant athletic offerings and each reported 11 head injuries across all sports for the entire school year.

“Maybe our numbers are low and next year they could be extremely high,” said Tom Giusti, athletic director at Newton North. “We take this very seriously, and we’ve provided all the education, in terms of knowing concussion signs and symptoms. We’ve been proactive about keeping kids out and having kids follow through with doctors.”

Marie DeSisto, director of nurses for the Waltham public schools, submitted the high school’s data to the state. She wrote down “92 known concussions,” but when contacted by the Globe said that was every concussion she knew about, both in and out of school. The number she had for sports alone was 54, which she didn’t put on the form.

“There’s still some confusion about what things mean,” said DeSisto, who is also Massachusetts director for the National Association of School Nurses.

Several perennial football powerhouses aren’t among those whose forms were released by the state, including Everett High School, Marshfield, and Xaverian,. This was the result, in some cases, to misunderstandings over the new requirement.

Everett’s athletic director insists he submitted a form, though it wasn’t included in the group released by the state. And Marshfield athletic director Lou Silva said he didn’t know why the state didn’t have his school’s form, since he expected another school staff member to submit the data. The Xaverian head coach said his staff filled out the form, but wasn’t aware it needed to be submitted to the state.

At the request of the Globe, Dr. Michael O’Brien, associate director for the Sports Concussion Clinic at Boston Children’s Hospital, reviewed the data received so far. He said the huge range in the numbers tells him there is probably underreporting by some students.

Several studies document that athletes are underreporting concussions, he said, by “either not recognizing it or, more often, not getting the message that concussion is a serious long-term injury.”

Dr. Lauren Smith, medical director for the state Department of Public Health, which is responsible for collecting the head injury data from schools, agreed that students have been hesitant to admit to head injuries, but she thinks that is changing because of better education.

“We’re in a transition period, where public awareness is increasing,” said Smith. “I expect an increase in concussion reporting.”