Failing schools have been turned around by sharing the same head teacher, an Ofsted report has said.
All the 29 federated schools visited in the survey by Ofsted have improved since they made the decision to federate, the watchdog said on Thursday.
Schools which have joined together to raise standards have seen improvements in teaching, learning, behaviour and pupils' achievement.
Despite previous concerns from parents over stronger schools suffering by joining with a weaker institution, Ofsted said they found "no evidence" to support these fears.
The report, 'Leadership of more than one school: An evaluation of the impact of federated schools' looked at a sample of the schools which had been joined under one governing body and in most cases, also shared an executive head teacher.
Ofsted's chief inspector, Miriam Rosen, said: "School federations play an important role, with effective leadership being the single most critical feature in helping generate and sustain improvement."
According to Rosen, the best leaders were focused on raising expectations, had rigorous procedures for holding staff accountable and continually assessing and improving teaching quality.
The report highlighted the benefits extended to pupils as well as teachers. Students were found to be more confident because they had a larger circle of friends, and those with special education needs and disabilities showed an improvement in achievement.
‘What we found noteworthy was the success leaders had when transferring these skills to federations which are larger and more complex to run than single schools", she added.
"I hope the best practice revealed in this report can provide inspiration and support for those schools considering a move towards federation."
Advantages of federations include schools being able to pool resources and increase curriculum opportunities. Some of the successful schools had been approached by local authorities to help a struggling institution whilst others were small schools in danger of closing.
The watchdog estimated there were more than 600 schools where leadership was shared through federation.