England could be facing a shortage of up to 19,000 school leaders by 2022 if action is not taken to plug the gap, it has been suggested.
Almost one in four schools across the country could be affected by a lack of headteachers, deputy heads and assistant heads, according to a report by three education leadership organisations.
It argues that an increase in pupil numbers and a rise in school leaders retiring and leaving the profession early along with increasing demand for senior staff to work at academy trusts means that more people are needed to step into top roles.
But currently, many schools are experiencing problems in recruiting staff, the report says, adding that while schools are estimated to spend up to £200 million a year on recruitment, many fail to find the quality of candidate they require.
It concludes that there are four main issues in finding school leaders: potential headteachers are put off by some of the challenges of the job; the profession lacks a culture of development and feedback; recruitment of headteachers is inconsistent; and leaders do not feel they get enough support or feel motivated to stay in leadership roles.
Overall, England will need between 14,000 and 19,000 more heads, deputy heads and assistant heads by 2022, the report says.
Up to 8,000 may be needed to meet a growth in leadership roles at academy trusts, while there is also a need for 2,000-3,000 more in the current school system. At the same time, the supply of school leaders is expected to fall by 8,000 due to retirement and staff leaving the profession early.
Secondary schools are currently the most affected, but by 2022, the issue will also be having an impact on primaries. Schools teaching the most disadvantaged students are the most likely to be hit by a lack of staff.
"These schools make up 40% of all schools in England but are likely to face half of the leadership shortage. By 2022, our most challenged schools may need up to 10,000 more school leaders."
The report, by the Future Leaders Trust, Teaching Leaders and Teach First, calls for a new generation of school leaders to be developed by supporting them to move up the career ladder.
It says that more should be done to support school leaders and improve perceptions of the role, and also suggests that the pool of candidates able to take on non-teaching senior roles could be expanded by looking at people outside the profession.
James Toop, chief executive designate of the merging Teaching Leaders and The Future Leaders Trust, said: "Great school leadership is essential for improving school performance and children's life chances, especially in deprived areas of England. We have worked closely with key partners - from individual schools to the Department for Education - to develop great leaders but this report is a challenge for us to do more.
"We must develop more leaders who are committed to educational equality and excellence, from middle leaders to academy trust CEOs. We need to ensure systematic leadership development is normal in every school so every child can achieve."
A Department for Education spokeswoman said: "We do not recognise these figures. The latest school workforce data shows that there are 68,800 FTE leaders in state schools in England. Furthermore, since 2010 the proportion of schools reporting a headteacher vacancy has decreased and the number of school leaders over the age of 50 has decreased significantly.
"However, we recognise that we need to work with the profession to ensure we can develop even more great school leaders. We are doing this through a range of professional training including the National Professional Qualifications, the High Potential Middle Leaders and High Potential Senior Leaders programmes to develop excellent leaders in challenging schools.
"We are also continuing to support the expansion of Teach First to recruit more top graduates with the potential to become future school leaders in some of the most challenging parts of the country."
Malcolm Trobe, interim general secretary of the Association of School and College Leaders, said: "Many more school leaders will be needed over the next few years and it is vital to take action now to address this issue.
"The Government and profession have to work together to ensure the right training and development opportunities are in place to encourage and nurture future leaders.
"To this end, ASCL is working with other organisations to set up a new foundation to support leadership development.
"We must also work together to send out positive messages about school leadership. It is, of course, a challenging role, but it is also a tremendously fulfilling one, and we hope that many teachers will step forward to seize the great opportunity to become the school leaders of the future."