Japan's classrooms are rapidly becoming places of fear.
Previously pupils may have dreaded violence from too strict teachers - but now educators themselves are saying they live in terror.
A record 1,609 teachers took a leave of absence in December because they were stressed by students' intransigence, said the ministry of education.
Increasingly common lesson disruption has become known as "classroom breakdown" and has taken Japan's once revered teachers by surprise.
The Japanese media is packed with reports from harassed teachers stunned by the spreading rebelliousness. NHK (Japan's equivalent of the BBC) recently devoted a six-part series called Destruction of the Classroom to the problem. One in 12 classrooms nationwide fell into this category, it claimed.
Discipline has rarely been a problem before. Traditional teaching methods, based on Confucian precepts, required total silence from passive students who at least gave a semblance of paying full attention. Pupils were often told they should be "like grave stones" - all the same and silent.
Now teachers are beginning to lose control of the classroom as Japanese children embrace more aggressive, individualistic American and European codes of behaviour, say sociologists.
Teachers say they are bewildered by disruptive or threatening behaviour.
But teacher violence also appears to be growing. Although physical punishment is prohibited by law, the ministry of education said a record 414 teachers were reprimanded for striking students last month.