When I was young, I used to be very active as an Adventurer, conducting training and bringing group of young people to climb Mount Ophir. Not a very tall mountain but still, periodically there are news of accidents and even death.
It is a great responsibility to lead a group of young people and I never brought anyone below 16 and full discipline is a requirement.
I am not sure how the climb of Mount Kinabalu is conducted but I will have great reservations to bring students of age 12 and below for mountain climbing.
Whether this accident happened or not, taking 12 year old to climb mountain and worse, cliff, is totally unacceptable by any standards.
I thought I was crazy enough to bring group of 17 and 18 year old students to climb Mount Ophir but I guess I was far more prudent than these schools.
As I have said, whether the Earthquake happens or not, sending 12 year old kids to climb cliff is really insane.
The key thing is about reducing risk or the amount of risk you take. It is true that Earthquake is not something you meet often and whoever caught in the Earthquake may face death.
However age does matter when it comes to handling emergency or crisis. At least I did train basic First Aid to my group of people but I doubt they gave such training to a 12 year old student.
If you want to take young children to mountain climbing, start with small camping skills first. Start with small group, with one instructor to 1-3 (max 5) students so to reduce risk due to negligence.
Risk management is about minimizing risks, not about having zero risk. It is apparent that in this case, age is a factor to risk.