A 49-year-old repairman from Northeast China's Heilongjiang province, whose employment contract with a primary school in Beijing's Xicheng district, was due to end this month, took revenge on the school, which refused to sign a new contract with him, by attacking students with a hammer when the pupils were taking their physical education class in the school playground on Tuesday morning. A total of 20 students were wounded, four of them seriously, according to a news conference organized by the Xicheng district government on Tuesday evening.

It is good that the district authorities in education, public security and medical care took part in the news conference presided over by the district head, and explained what had happened and what they had found in their investigation, as it helped to dispel public anxiety and nip rumors in the bud, as some social media posters were prepared to turn the breaking news into a sensational selling point.

Nevertheless, there are lessons to be learned from this tragedy.

This is the first time that a violent attack targeting students happened at a school in the center of Beijing, where campus security work has long been regarded as the best in the country.

Unlike previous indiscriminate assaults on schoolkids, which have usually happened outside the school gates when the children leave to go home and which have been carried out by people unrelated to the school, the Xicheng attack occurred in the school while the children were having a PE lesson and was by an employee of the school. Since the security staff of primary schools are not prepared for an insider attack such as this, it rendered all of the school's security efforts useless.

Thus it is necessary for the Xicheng government to urge all schools to draw lessons from the incident, which would have been avoidable if the school had paid attention to the emotional state of the middle-aged repairman, who was soon to lose his job, and acted with more consideration while informing the man of its decision not to extend his contract.

Such thoughtfulness is necessary to ensure all employees working in primary schools, have suitable temperaments to work in what are special, and to some extent closed, environments. It takes special training to become a teacher. But the repairmen and employees working in other non-teaching posts in schools, such as canteen staff and those working in the warehouses and maintenance departments of schools do not receive any special training even if they have daily contact with the children.

The school is obliged to ensure the security of the students, and it has no reasons to ignore a member of staff angry at perceived mistreatment.

The parents also have every reason to ask why the PE teacher and other members of the staff did not act, and why some schoolteachers instructed them to not to talk about the incident. It is to be hoped the lessons from this tragedy are learned by all schools.