ASheffield secondary head is describing the era of cut-throat competition between schools - a period ushered in by open admissions, local management and league tables: “I remember, as a deputy, explaining a new curriculum innovation to a staff meeting and warning them not to breathe a word to anyone who worked in the school down the road. We didn’t want our competitor pinching our ideas.”

Now, the same head says: “I’ve been enabled to break out, mix with other heads on a friendly, mutually supportive basis. I have the confidence that I can go to any of the heads about an area of concern and say, ‘Can you help me?’”

The change is a result of the Government’s leadership incentive grant (LIG), in this case managed by a forward-thinking local authority and some visionary heads. When it started in 2003, Sheffield already had some experience of schools working together, developed by Excellence in Cities which created groups that included schools with high, low and average raw exam scores. These groups took on the LIG challenge of working together to improve leadership and management, and raise achievement. Their experience may be crucial for schools planning to collaborate using the new trust status.

The diversity of these groups was crucial, since what happens when schools collaborate is far more subtle than the donor-receiver model suggests.

Heads report a win-win situation when their staff work in and visit other schools. Where teachers see excellent practice elsewhere, they can bring back ideas and resources. If what they see is less good, then it boosts their self-esteem.

But the Sheffield heads said the most significant factor in raising standards and improving leadership was regular supportive and challenging meetings.

Heads have always met other heads, but the LIG meetings are different. “In formal meetings, you never really get a feel for what they are like as heads - as human beings interacting in quite difficult situations,” said one. “I feel in the small LIG groupings - and subsequent meetings - you get more of a feeling of how this human being is coping with an extremely difficult task we’re faced with. That’s very reassuring,”

Others said hearing heads talk frankly about how they lead and manage their schools can help colleagues to extend their leadership toolkit.

The most effective leaders can respond flexibly to ever-changing situations. But people are most comfortable in their preferred management style, and while they might be able to work differently when necessary, they probably revert to their norm quickly - even if that is not really what is needed.

A related idea would be a head who brings a school out of special measures in an authoritarian way, and then continues in the same vein, but gets frustrated because the same approach fails to take the school any further forward.

Some heads are better than others at looking beyond their own schools: One said: “When you start - particularly in a school that’s got problems - you’re very much nose to the grindstone. People in successful schools have got time to get their head up and look around.”

LIG meetings allow these heads to share their insights. But heads of successful schools said that when they needed to improve in a particular area - say, tracking students’ academic progress - the schools most likely to have effective procedures were those that were, or had recently been, “under the cosh”.

There may still be some way to go to reach the point at which all heads understand and value collaboration.

In the past couple of years, a colleague working towards the National Professional Qualification for Headteachers told me that the head tutoring his cohort had opened their first session with a video promoting his own “successful” school, boasting that he had “closed down” two nearby schools.

As long as such people are running schools and - worse - are responsible for developing the heads of the future, there is work to be done in promoting the huge benefits of “deep collaboration” between schools. And continued funding with collaborative strings attached would not go amiss.

Phil Taylor, a former head, now works as a school improvement partner and consultant