By Sean Coughlan
BBC News education reporter
Whenever a politician wants to talk tough, a speech about classroom discipline is never far away.
Classroom discipline is a popular theme for politicians
David Cameron, assailed by leadership doubts, set out his own no-nonsense credentials with a speech that called for head teachers to be given more power to control and exclude disruptive pupils.
Feckless parents were also under scrutiny - for failing to back up the school and needing to sign enforceable contracts before their children will be admitted to a school.
When Ed Balls entered the fray as the new Children, Schools and Families Secretary, he also talked about getting tough on unruly classroom behaviour and teaching lessons in respect.
And the secretary of state he replaced, Alan Johnson, had only just announced "a new three Rs: rules, responsibility and respect".
No one has ever lost any votes by promising to improve school discipline - and focus groups, commissioned by the education department, showed earlier this year that discipline is the biggest school issue for parents.
"Politicians like talking about classroom discipline - they can use it as a metaphor for wider problems in society and a way of sounding tough on law and order," says Mary Bousted, general secretary of the Association of Teachers and Lecturers.
David Cameron says pupil referral units are not working
"It's a perennial theme - a way of talking about education that the wider public can understand."
But what difference do all the announcements make?
The proposals made by Mr Cameron on Tuesday - such as scrapping external appeals panels for exclusions and introducing enforceable home-school contracts - have been Tory policy since Iain Duncan Smith was party leader.
In opposition, they haven't had the chance to put the theory into practice.
But there have been no shortage of "crackdowns" and "zero tolerance" announcements from the government, promising an answer to anxieties over unruly pupils.
Mr Cameron has now condemned one of the most widely-used approaches - the pupil referral unit - as an expensive failure.
Mary Bousted says schools are places of security for troubled children
There are about 450 of these units in England, teaching pupils who have been excluded from mainstream classes and helping to reform their unacceptable behaviour. There were 15,240 pupils in these units last year - with a further 8,430 using such units alongside other institutions.
The need for such an alternative for excluded pupils is part of the difficulty for any tough talking.
If there is a crackdown on behaviour and the unruly are to be thrown out of the classroom, there is still a legal obligation for these pupils to be given an education.
And if one school is energetically improving behaviour by chucking out disruptive pupils, does that mean that another school will end up picking up the pieces?
Last year, in England, there were more than 1,700 pupils excluded every single school day. Of these, about 45 each day were permanent exclusions.
The call from Mr Cameron to make parents sign up to a behaviour contract before starting school is an attempt to make families aware of their responsibilities. Sign up and promise to behave, or else there is no admission.
But it's often the most dysfunctional families who are going to present the most difficulties. And how are they going to be made to comply?
Such legally-enforceable admissions contracts could end up as a "bureaucratic nightmare" for schools, says Dr Bousted.
Bad behaviour is often a complex, deep-rooted social problem - often nothing to do with school at all - and is far from straightforward to change.
The government in its first flush of optimism announced a target to cut truancy by a third. But, unlike the children concerned, the problem showed no sign of disappearing.
There have been repeated warnings and initiatives over truancy - including fines and imprisonment - but it hasn't solved the problem. Pupils with the most unstable, chaotic home lives are the hardest to reach.
"There are children facing family break-ups, those who already have responsibilities for childcare, children with horrendous family backgrounds, those taking drugs, those living in the roughest social housing... they're going to be at school the next morning," says Dr Bousted.
Schools have the task of socialising the pupils where the rest of society hasn't succeeded, she says.
For such children, schools can often be the only secure places in their lives - and Dr Bousted says that teachers can be very cynical of politicians using schools as a way of bashing home a law and order message.
Disruptive behaviour might also reflect more complex issues, she says - such as whether the curriculum is relevant or whether a secondary school is too big.
"Unfortunately the only school where you can wave a magic wand to solve behaviour problems is Hogwarts," said the Schools Minister, Kevin Brennan.