New school structures such as federations, academies and trusts can improve the performance of heads, but they can also disempower and demoralise them and add to pressure on classroom teachers, according to new research.
All three structures were recommended by ministers last week as ways of fixing England's low performing secondary schools.
The study, carried out by Manchester University for the National College for School Leadership, found that the job of senior management was changing rapidly as a result of government policies.
Headteachers were collaborating and working with outside partners more because of the new types of school, which also provided some with new career opportunities.
But the research found that, in other cases, heads had felt "disempowered and even demoralised".
"Some have reported that federating has reduced the power, autonomy and status they previously enjoyed, without reducing the pressures - indeed the pressure to succeed may seem even greater," the study says.
The researchers conducted 20 in-depth studies, each looking at four examples of secondary federations, trusts, all-through schools, academies and schools where heads had delegated and distributed their responsibilities to other staff.
They found that restructuring could increase opportunities for deputy and assistant heads.
But the new types of school organisation often came with higher expectations from inside and outside the school. In one academy, the researchers found that some staff talked of being under enormous pressure to improve their exam results and complained of a lack of support.
One teacher said if they called senior management for help over a disciplinary matter, they were likely to be asked for their lesson plan. Another young colleague said everything was done for the pupils.
The report says: "Some increase in attention and expectations is inevitable in times of substantial, even radical, change to the organisation of schools.
"However, it is important that, at senior levels, leaders are aware of the impact such expectations may have on classroom teachers, and have positive strategies to ensure these do not turn into unreasonable pressures."
The study said more research was needed to investigate whether the new structures had any impact on pupil progress. But it found they could improve school leaders' performance and experience at work, and help them deal with the increasingly complex nature of the education system.
The research concluded it was possible to combine innovative frameworks for school governance with a traditional approach to leadership and management.
"Successful leaders do not lose sight of the need to pay close attention to the quality of the core teaching and learning tasks, even when they delegate the day-to-day management of that function to other leaders," the report says.
'Emerging patterns of school leadership' is at www.talk2learn.co.ukmedia58A7Femerging_patterns_ school_leadership.pdf.