Yasuhiko Kobayashi’s 15-year-old son had skipped judo practice.

According to Kobayashi, the boy’s teacher was furious and stood waiting for him at the gates of his junior high school in Yokohama. The teacher forced the boy into the gym and made him grapple one on one. The former All Japan judo champion choked the boy until he lost consciousness.

When the boy came to, the teacher choked him again until he went limp, and threw him to the floor with such force that he suffered severe internal bleeding in his brain, an injury known as an acute subdural hematoma.

The injury incurred on Dec. 24, 2004, left Kobayashi’s son unable to remember anything for almost two years, while the teacher was later transferred to another junior high school in the city in accordance with standard job transfers among public school teachers.

The incident alleged by Kobayashi’s parents is one of a spate of similar deaths and injuries in school judo classes in recent years reminiscent of the beating death of young sumo wrestler Takashi Saito during a disciplinary “training” session in 2007.

The parents of Koji Murakawa, a 12-year-old junior high school student in Shiga Prefecture, allege their son died from a similar injury in July 2009.

Murakawa complained to his instructor he had asthma. He was told to wear an antidust mask and made to spar with the instructor. The teacher reportedly violently threw him to the ground, also leaving the boy with a subdural hematoma.

Taken to a hospital, Murakawa was later pronounced brain dead. His body was covered with bruises, according to his parents.

“Subdural hematomas occur when the connection between the brain and the skull loosens and stretches the bridging vein,” explained Dr. Masato Noji of the neurosurgery department at Ashigarakami Prefectural Hospital in Kanagawa Prefecture.

“The result is severe internal bleeding within the brain. Such injuries are extremely traumatic and usually fatal. As a ringside boxing doctor, I was extremely surprised to learn that these sorts of injuries come from judo practice in schools.”

Dr. Ryo Uchida of Aichi University of Education is concerned about the frequency of deaths in school judo classes.

“Over the 27-year period between 1983 and 2009, 108 students aged 12 to 17 died as a result of judo accidents in Japanese schools, an average of four a year,” Uchida said. “This is more than five times higher than in any other sport. About 65 percent of these fatalities came from brain injuries. This is clear evidence of a dangerous trend in Japanese schools.”

The statistics are doubly alarming because they have no parallel in other developed nations.

A representative from the British Judo Association said, “to our knowledge, there have been no deaths or serious brain injuries in judo in the BJA.”

Dr. Robert Nishime, chairman of USA Judo’s Sports Medicine Committee, points to a dearth of safety procedures for judo classes at Japanese schools.

“There have been no known traumatic brain injury deaths attributed to judo for all participants under the age of 18,” Nishime said. “So there appears to be a significant difference in serious brain injury rates in the youth between the U.S. and Japan.”

Kobayashi, the father of the 15-year-old Yokohama boy, complained that the parents of children killed or severely injured in judo practice have been met by a wall of silence when pressing for convictions of the alleged perpetrators.

The police sought charges against his son’s teacher, but prosecutors dismissed the case. A judicial inquest panel concluded the dismissal was unreasonable, but prosecutors threw the case out for a second time.

“Not a single incident has resulted in criminal prosecution,” Kobayashi said.

In another incident, the parents of Ryo Tozawa, a first-year student at a high school in Akita Prefecture, allege his judo coach asphyxiated him in 2003 despite the boy’s pleas to stop. Prosecutors twice declined to follow up on the boy’s death after police pressed for charges.

Kobayashi and Murakami’s families founded the Japan Judo Accident Victims Association on March 27 to support victims and their families, and to lobby for improved training safety. They will hold a symposium in Matsumoto, Nagano Prefecture, on Sept. 12 to tie in with the World Judo Championships being held in Tokyo from Sept. 9 to 13.

One concern of the association is that new national curriculum reforms, known as Ikiru Chikara (The Zest for Living), will require all junior high school students to practice sumo, judo or kendo starting with the 2012 school year.

A 2009 All Japan Judo Federation study found that about 70 percent of junior high schools in Tokyo and Ibaraki Prefecture plan to make judo compulsory in 2012.

This concerns Uchida, who said he is unaware of any recent safety improvements and believes instructors have little regard for safety.

“As of 2012, it’s difficult to anticipate to what extent mortality levels will rise,” Uchida said.

However, because girls will also take part, the number of students participating in judo classes will roughly double.

“Consequently, without safety improvements, we can expect the mortality and serious injury rate to double accordingly,” he said.

While the All Japan Judo Federation remains silent on the issue, the head of the instruction department at judo’s spiritual home, the Kodakan Judo Institute in Tokyo, has been unable to hide his concerns.

Writing in the August issue of Budo magazine, Mikihiro Mukai argues: “Until now, the judo world has tried to hide things they perceive will be disadvantageous to them. But this trend will worsen the situation, even if we have many discussions about instruction methods, if there is even a single case of death or severe injury, that method is inadequate.

“There may well be some unfortunate accidents, but we as judo instructors must work to eradicate such problems,” he wrote.