Simple defiance is one thing, but this kind of mutinous behaviour is the stuff of nightmares. By publicly calling your authority into question, this pupil is sending a clear signal to you and her classmates that she thinks you are not worthy of being taken seriously.
Although it only takes one pupil to say something, this is probably a signal that discipline is not strong enough throughout the class. It is a situation that could become sticky, but confident handling will usually defuse it - and earn you some respect along the way.
Tom Bennett, head of religious studies at Raine's Foundation School in east London, is unequivocal about the intentions behind remarks like this. "Any pupil who criticises the teacher about their professional standards in the classroom isn't doing it to provide positive feedback," he says. "They're doing it to undermine you, and they know it. It's disruptive behaviour masked as conversation."
He adds: "The day my pupils have a postgraduate degree in education is the day I'll listen to their opinions on teaching methods. Until then they can button it."
Their criticisms might not be worth hearing, but that doesn't mean you should ignore the message this behaviour sends. "If you've got to a situation where a pupil is confident enough to stand up and say that, there's a strong possibility that it's true," says Jon Berry, senior lecturer in education at the University of Hertfordshire. "You have probably reached a point where it's beyond your competence to deal with it."
Teachers are all too conscious that a moment like this can mark a shift in the balance of power in the classroom. But resist the temptation to panic and fight fire with fire. Using sarcasm or trying to humiliate your aggressor will only begin a draining and futile battle. It also sends the signal that this is an acceptable way of talking to people.
Mr Berry suggests using the school's disciplinary procedures to caution the pupil. But next time this situation arises, you can be better prepared to deal with it.
Victor Allen, behaviour consultant at Mirror Development and Training, advises a brief and assertive answer. "Be an authority. Somebody needs to be in charge."
He warns that if pupils don't get a firm line from their teacher they will look to their peers for a standard, and play to the crowd. "They'll have one eye on you, and they'll have one eye on their friends," he says. "It's `look at what I've done'."
Tell the pupil you won't tolerate that kind of behaviour in your classroom. Invite her to discuss it with you, but "at my time, in my way, and with my rules, not yours", as Mr Allen puts it. If she continues to be disruptive, take her outside. It's a question of confidence.
If you're worried one of your classes is on the verge of slipping out of control, turning up with a strong lesson plan will give you a head start. Knowing what should be happening at every stage will bolster your confidence, and clear tasks mean that you can give troublemakers short shrift by referring them to the work at hand.
In the long term, building relationships with pupils is the key to effective discipline, but they need to learn early on where the boundaries lie. Mr Berry says that teachers who are starting out often have trouble with children they see their more experienced peers enjoying cordial relations with, because they treat them too leniently at first.
"The harshest lesson teachers learn when they come into the profession," he warns, "is how to subjugate the nice, caring person who lives inside their skin."
Next week: Awkward social situations.