A lack of effective teacher monitoring and inspection has also been cited as a problem.

"Ethics are most important for educators. A teacher with an unsound personality and mind is a time bomb," said Sang Qingsong, an education researcher at Anhui Normal University.

Education departments should do more to vet their teachers and ensure they have strong ethics, Sang said.

In mid-May, Vice Minister of Education Liu Limin urged local authorities to be strict about school safety and tighten oversight of kindergarten, primary and middle school teachers.

Unqualified teachers should be transferred to other posts and those who break the law or are otherwise unethical must be weeded out, Liu said.

Many male teachers are young and do not know how to treat girls appropriately, said Yi Yun, principal of the primary school He's daughter attends.

School authorities typically tell young teachers not to be alone with children and to avoid physical contact, Yi said.

A moral decline that has emerged alongside economic and social development should also be blamed, said Qin Qianhong, a law professor at Wuhan University in central China's Hubei Province.

Qin said legal deterrents should be enhanced to discourage potential offenders. While a rape conviction can result in a death sentence, the crime of prostituting girls, which molesters are usually charged with, brings a sentence of 15 years in prison at most.

"The nature of sexually abusing girls is very bad. Such culprits deserve a death sentence," said Liu Fei, a public servant in the city of Jinggangshan in Jiangxi.

"In many cases, the offenders are punished and convicted of the crime of prostituting girls. This is absurd and reduces the penalty for committing illegal acts," Liu said.

In response to the cases, the Supreme People's Court (SPC) vowed to take a zero-tolerance approach to crimes that harm minors, as well as called for harsher punishments for such crimes.

Tang Sulan, a writer in central China's Hunan Province, has called for the establishment of government-led protection systems for minors that feature the participation of legal and education authorities, as well as non-governmental organizations.