As I visit schools up and down the country, I am constantly struck by the ways in which some are seizing the opportunities presented in these fast-changing times. In particular, I see school leaders stepping up to take on a greater role by helping other schools to improve. This is manifesting itself in a number of ways, through federations and trusts, through teaching school alliances, through the work of national and local leaders of education and, increasingly, through chains of schools.

Chains are a relatively new concept, but since the first was created less than 10 years ago, they have grown rapidly. While they currently account for about 3 per cent of our schools (or 10 per cent of secondary schools), plans for continued growth in the secondary sector and expansion into the primary sector mean that they are becoming a familiar approach to how our schools are led and managed.

To find out more about this growing phenomenon, the National College has just published a major piece of research, led by policy analyst Robert Hill. It provides a detailed analysis of how many schools and academies are in chains, how they are led, their plans for expansion over time, and the opportunities and challenges presented for those involved as well as for the wider school system.

The growth of chains is increasingly driven by school leaders. The majority of the more recent “sponsored” academy chains are led either by successful schools or by other educational providers, such as further education institutions. Others are forming or joining “converter chains”, groups of schools that want to work together as they convert to academy status. This is an important development because it is moving away from the perception of chains as a deficit model, whereby you join a chain only if you are in trouble or vulnerable.

The research also indicates that sponsored academy chains are having a positive impact. Early evidence shows that they are making significant improvements in GCSE results compared with stand-alone academies. And Ofsted results are equally encouraging: sponsored academy chains have a higher proportion of schools classified as outstanding than non-chain academies.

However, it is early days for chains and it is clear that some are developing more effective platforms for improvement than others. The best ones have a shared vision across their schools, with robust governance and clear lines of accountability that balance central direction with local discretion. They keep a strong focus on improving teaching and they make use of their scale to develop staff and move them around the chain to where they can make the most difference. Of course, that is not to suggest that chains are a panacea or that joining a chain is a guarantee of success. Many schools will want to work in other ways. This isn’t a one-size-fits-all approach.

Supporters of chains see them as the best way to ensure that weak schools are supported as more schools become academies and as the role of the local authority changes. They argue that expecting every individual school to have excellent leadership and governance is a tall order, so why not make the most of the best leadership and governance across a chain of schools? Many go further and see a future in which large chains with strong brands compete with each other and offer real choice for parents.

Others are concerned that academies that are part of a chain may lose sight of their particular context and have a reduced focus on their local community. There are also concerns that those who lead a school in a chain may have less autonomy than they would have as part of the local authority.

My own view is that I share the concern about the importance of the local context, but overall I think that academy chains are a positive development within our education system. They are making the most of strong leadership and governance, they are developing capacity for improvement within and across schools and they are making a significant contribution to raising standards, often in the most challenging circumstances.

But the research also identifies some pressing issues that need to be addressed. Many chains are expanding rapidly, in particular as they take on underperforming schools. Experience from other sectors shows that such growth needs careful management so that capacity does not become overstretched, risking the failure of one or more schools in the chain. If leaders focus too much on acquisition and not enough on building capacity within the chain, they may come unstuck.

Moreover, there is a danger that chains could become “islands of educational excellence”, only concerned about the schools in the chain rather than playing a role in supporting and driving improvement more widely.

There are also longer-term challenges that need to be considered. These range from securing a supply of executive leaders with the skills and qualities to lead chains, through to ensuring that chains are held accountable for their performance.

These are interesting times and the educational landscape is shifting. We must continue to debate the fundamental issues and, in doing so, constantly challenge ourselves to ensure that every school gives children the best possible start in life.

Steve Munby is chief executive of the National College for School Leadership. For further information and to download a copy of The growth of academy chains: implications for leaders and leadership, visit www.nationalcollege.org.ukacademychains.