Haircuts, contributors to The TES online staffroom believe, are a reliable indicator of a child's abilities and behaviour. Proposing this theory, one teacher said: "Show me a boy with a Nike arrow shaved into his misshapen bonce, and I will show you a pain in the ass."
According to this theory, the suspension last week of a 14-year-old Merseyside schoolboy for having an "inappropriate" Beckham-esque hairstyle, was not so much a punishment as an act of pre-emption. A pupil's enthusiasm for follicular self-expression is a clear warning of a tendency towards self-expression in other, more obtrusive ways.
One contributor said: "A central "range" of peaks, leading from neck to the narrow flatlands of the forehead ... usually adorns a pupil standing hunched against a wall outside the office at playtime, radiating resentment at being told off."
Another agreed: "My horrible boys are all having their hair highlighted this weekend. And they all have sticky-up fringes."
But parents, who fund the heady triumphs, are not pleased at such judgments.
Margaret Morrissey, of the National Confederation of Parent Teacher Associations, said: "To stereotype a child because of a haircut is very harsh. If this were done to teachers, they would be absolutely mortified, complaining that it's their right to have any hairstyle."
Poor expectations resulting from prejudice, she said, lead a child to misbehave. If schools demand tamed tresses from pupils, the issue should be discussed with parents early in the admissions procedure.
Today's yob signifier may also be tomorrow's conventional style. Nicky Clarke, the celebrity hairstylist, cites the close-crop "buzzcut", initially associated with skinheads, but now an acceptable part of mainstream culture.