Thank you for the question about Kendo.

I don't have statistics for accidents in other school sports in Japan, but as far as I can tell Judo is bar far the most dangerous.
Falls and throws are a normal part of Judo, but in too many cases in Japanese schools they have resulted in serious injury or death.

To take 2 examples (out of a list of 110) from the site that I mentioned in my previous post [http://judojiko.net/eng/]

2002, 8th grade male student
On the day of the accident, the judo team had a joint practice session with teams from other middle schools from 9:00. At around 10:21, they started kakari-geiko
(3 min x 6), and the victim practiced with a student from a different school. When he was thrown with osto-gari, because his partner fell with him, he hit his back, head, and stomach hard on the mat.
Thereafter, they resumed the match, and at around 10:24, the partner threw the victim again with osto-gari. This time, he hit his back and head and became unconscious.
The teacher in
charge put a cold wet towel on the victim's forehead and watched him for a while. As he did not regain consciousness, the teacher called an ambulance and his parents.
The victim was
taken to a medical institution and treated with a mechanical ventilator at the ICU; however, he became brain-dead the following day and died 3 days after the accident.

Cause of death: acute subdural hematoma

2003, 10th grade male student
On the day of the accident after warm-up, stretching, and ukemi practice, the victim did 50 uchikomi with a partner. Thereafter, he did randori with another student and was thrown with migi-seoinage (right shoulder throw). Right after the fall, he stood up but then fell forward on his stomach. He was taken to a hospital and diagnosed with acute subdural hematoma. He later experienced symptoms such as profound coma, cessation of natural breathing, dilation of the pupil, and no brainstem response. He was declared brain-dead and he died after 8 days.

Cause of death: acute subdural hematoma

Judo contains very dangerous actions that are not allowed in other sports.
To take the case of rugby for example:
The International Rugby Board's rule on 'spear tackles'
reads: "It is dangerous play to lift a player from the ground and drop or drive that player into the ground whilst that player's feet are still off the ground so that the player's head and/or upper body come into contact with the ground."

Clearly when children are engaging in Judo they require careful, expert supervision. The number of deaths and serious injuries thus far indicates that this has not been the case in Japanese secondary schools. Without proper training of staff, making the sport complusory instead of optional can only make matters worse.

Robert Aspinall
Shiga University