The Ministry of Education urged schools and kindergartens to improve their security arrangements on Wednesday, the day after a school principal was killed.

In a set of guidelines, the ministry said that improvements in safety management should be made in accordance with students' ages, and physical and mental characteristics.

"Security guards in our school are told to pay special attention in the morning when students enter the building so they can detect any intruders," said Yang Jie, a high school teacher in the Xicheng district of Beijing. Her school is strict about registering visitors.