Mike Baker BBC education correspondent

In rugby it's called "getting your retaliation in first". It can be effective but it does not endear you to opponents or spectators.

It might prevent any planned aggression against you. Or it might provoke more. In short, it is a risk.

So why did the Education Secretary, Estelle Morris, make a pre-emptive strike against the teacher and head teacher unions? After all, she is not normally the aggressive type.

The alternative to co-operation, she said, was "to return to the dark ages of dispute and conflict"

In case you missed it, the education secretary used a speech this week to warn the teacher unions against industrial action.

Her message was stark, almost Thatcher-ite, in tone: you are either with us or you are against us.

The alternative to co-operation, she said, was "to return to the dark ages of dispute and conflict". She didn't want to see the progress made "undermined by irresponsible action".

Estelle Morris can be tough. Anyone who saw her fight back, off the cuff, when delegates at the NUT annual conference walked out on her will know that. But she doesn't normally pick a fight.

So why did she choose to stir up the unions this week? She may have guessed, rightly, that the London branches of the NUT would endorse a call for a one-day strike next week, and so believed she had good reason to stand up for parents and children.

Limited strike

Well, the NUT is holding a one-day strike - its first for many years over pay - in London next week. But the turn-out in the ballot was small, only around 30%. A few parts of London will be affected for one day.

The strike will involve a small number of members in a single region of just one of the four classroom teachers' unions. Was this sufficient cause for antagonising the entire teacher profession?

Perhaps the timing of her attack is linked to the fact that we are coming up to the teacher unions' annual conference season. It is one of the few times of year when the teacher unions manage to set the news agenda, usually with attacks on government policy.

This uncharacteristic aggression may, I suspect, prove counter-productive

Meanwhile, Downing Street has been going through one of its periodic pushes to speed up the reform of public services. It sees the unions as a major obstacle to the public-private partnerships it wants to promote.

So I suspect Estelle Morris was taken aside by Downing Street and advised that, as she was about to get roughed up by the unions anyway, she would do well to stick the boot in first.

Her attack on union militancy helped give publicity to the NUT ballot result which came out later that same day, turning it from a local news story into a national one.

This uncharacteristic aggression may, I suspect, prove counter-productive.

For a start, the NUT seems to have considerable public support on this one (although taking it beyond a one-day strike might change that). Parents in the south east of England are very aware of the effect on their children of teacher shortages.

Puzzling decision

Of course, a strike won't solve that shortage but it does highlight the case for a bigger London allowance. After all, the public might wonder why a police officer gets a London allowance of �6,000 a year but a teacher gets just half that despite facing the same additional costs of living in the capital.

More puzzling still was Estelle Morris's decision to pick a fight with the head teachers. The trigger seems to be the decision by the two big head teacher associations, the NAHT and Sha, to ballot on a proposed boycott of the government's performance-related pay scheme.

This is remarkable in itself: it is the first national ballot by the NAHT for over 20 years and the first ever for Sha. But what exactly is it about?

If you recall, the government recently introduced a performance-related pay scheme which allows experienced staff who pass a quality test to move onto an extended pay scale. Last year was the start of the scheme and the majority of those eligible to apply did so and earned extra money.

The maximum classroom teachers' salary is beginning to look attractive to graduates

This was actually a triumph for the government since the very idea of performance-related pay had been fiercely resisted by the teaching profession. To be blunt about it, once teachers started to get the extra money the controversy over the scheme largely withered away.

The government could claim a victory: it had "modernised" the profession and has ensured that the maximum classroom teachers' salary is beginning to look attractive to graduates choosing a career.

The problem this year relates to those teachers who moved onto the first rung of performance-related pay last year and now want to progress further.

The head teachers say the government has only provided about half the money needed to allow teachers to move onto the next rung.

Parents unaffected

In other words, only half of the 200,000 eligible teachers can get a further pay rise. The head teachers say they should be able to reward all who deserve it. The government says managers in every other sphere of work have to ration pay incentives within budget limits. Hence the stand-off.

The head teachers' proposed industrial action will not affect pupils or parents as no child will be sent home and no-one will refuse to teach a class. The heads are only proposing to refuse to implement that part of the performance-related pay scheme which relates to teachers who have already passed the first "performance threshold".

At first it is hard to see why the government is taking them on. After all, ministers have already won the big battle over the acceptance of the principle of relating pay to performance.

This is all about getting head teachers... to operate within the funding that is available

The truth is that Downing Street sees the head teachers' stand as a further example of the intransigence of public sector attitudes.

The government wants more private sector management in the public services, including education. It knows private management will not operate with "blank cheque" pay arrangements.

This is all about getting head teachers, as managers of school budgets, to operate within the funding that is available rather than on an expectation that all who deserve a pay rise should get one. As Downing Street sees it, this is living in the real world of private sector constraints.

There is much lobbying going on at present over public-private partnerships. The unions fear the erosion of employees' rights and private business does not want to be bound by public sector rules.

It is this bigger political game which lies behind Estelle Morris's uncharacteristic attack on the teachers and head teachers. There will be more retaliation to come.