The stage was set, the lights went down and in a suburban Japanese primary school everyone prepared to enjoy a performance of Snow White and the Seven Dwarfs. The only snag was that the entire cast was playing the part of Snow White.

For the audience of menacing mothers and feisty fathers, though, the sight of 25 Snow Whites, no dwarfs and no wicked witch was a triumph: a clear victory for Japan's emerging new class of “Monster Parents”.

For they had taken on the system and won. After a relentless campaign of bullying, hectoring and nuisance phone calls, the monster parents had cowed the teachers into submission, forcing the school to admit to the injustice of selecting just one girl to play the title role.

Across Japan teachers are reporting an astonishing change in the character of parents, who, after decades of respectful silence, have become a super-aggressive army of complainers. The problem is that nobody can decide whether this is a good thing or not. Japan's mass media has opted to demonise them: a lavish television drama starting next month will present the monster parents as a vile symptom of a society that has lost all respect for its traditions and decorum.

The parents believe that they are champions of basic consumer rights, rights that Japanese society has supposedly long trampled over in the name of conformity and order. Either way, few deny that mothers and fathers have shifted from being staunch supporters of Japan's rigid education system to its most ardent assailants. Previously, when a child was in trouble the parents apologised profusely to the teacher; nowadays, they try to have the teacher sacked.

Where previously schools were trusted and respected, they are now the targets of concerted activism. Dozens of educators have been forced to resign in the face of the blazing fury of parents who no longer tolerate anything that appears to disadvantage their offspring.

In a new book on the phenomenon, Yoshihiko Morotomi, of Meiji University, lists hundreds of incidents that illustrate it. There are parents who have secretly placed recording devices in their children's classrooms, and others who have demanded that the results of sports events be changed to reflect expectations rather than the reality on the field.

In one case the mother of a child who was injured in the playground demanded that the child who accidentally caused the injury be suspended from school for as long as it took her son to recuperate - so that he would not benefit from the lessons her boy was missing.

Within the category of monster parent Professor Morotomi identifies the most potent strain: the “teacher hunters”, who conspire in small groups to ensure that a particular teacher is dismissed. Occasionally, he said, this involves physically mobbing their victim at the school gates and screaming abuse until a letter of resignation is signed on the spot.

“The monsters are created in family restaurants and coffee shops — places where the mothers meet each other to talk and relax,” said Professor Morotomi. “Simple chats spiral into ‘emergency meetings'... the conversation becomes more emotional and radical and suddenly what began as a simple complaint becomes a monsterised army of parents.” The sudden switch marks what many believe is the symptom of deeper social troubles at the heart of Japan, a transformation that took root during Japan's long economic downturn of the 1990s and whose effects have only now erupted.

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