Supply teacher spend exceeds £800m
Primary and secondary schools in England struggling to recruit teachers spent £821m on supply staff last year, it has emerged.
Analysis by BBC News shows the equivalent of £168 was spent on each child in order to hire in extra staff to cover vacancies and absences.
Teachers unions say the amount of money spent reflects a "serious teacher recruitment and retention crisis".
The government said the number of quality teachers was at a record high.
The latest data for schools in England shows spending on supply teachers accounted for 6% of the total amount spent on teaching staff wages. The overall figure spent on supply teachers fell by £18m on the previous year.
Schools in London collectively spent the most on supply teachers. Primary and secondary schools in the capital spent £212m on extra staff, the equivalent of £260 per child.
The Robert Clack School, in Dagenham, east London, spent the most on supply teachers in England. According to the government's data the school spent £953,807 on extra staff - the equivalent of £526 per child.
Dr Neil Geach, the school's chair of governors, said the figures included expenditure on counselling staff, extra-curricular sport staff and professional development spending.
"The figures as reported do not reflect reality... We do not use unqualified staff or cover supervisors to cover teaching groups - our children's education is too important."
Aside from London, Yorkshire and Humberside had the highest spending rate for supply staff of £161 per pupil, followed by schools in the West Midlands, which spent £160.
Schools in the East of England spent the lowest amount per pupil - £137 for every child.
Graham School in Scarborough, North Yorkshire spent £556,776 on supply teachers during the course of 2014-15, which was the highest amount in Yorkshire and Humberside.
Two years ago, the school was in special measures owing to its poor performance and as a result the new head teacher Helen McEvoy said she had to replace 45% of the teachers who were working in the school.
"Yes we have spent on a lot on extra teachers but that reflects the successful journey we've been on coming out of special measures," she said.
"Our use of supply teachers reflects how in the past we've had a lot of vacant posts and that's because it can be hard to attract teachers to come and work in a remote part of the country."
Government figures for 2014 show that teacher vacancy rate across England stood at 0.3%, which meant about 1,000 posts were vacant.
Teachers unions have expressed concerns about the use of private supply teacher agencies, claiming that some firms are putting the pursuit of profit ahead of providing high quality teachers.
The BBC found schools spent twice as much on buying in extra staff through private agencies than sourcing additional staff through local councils.
Becca Morgan, who set up the supply agency Principal Teachers in Catterick 16 years ago, said her company was currently experiencing its busiest ever period.
"We start dealing with schools looking for supply teachers at 6.30 in the morning and I often stop answering calls at midnight. To put it bluntly without companies like mine the reality is that the education system would grind to a halt."
Chris Keates, the general secretary of the union NASUWT, said the spend on supply staff reflected a "serious teacher recruitment and retention crisis".
A spokesman for the Department for Education said: "Supply teachers provide a valuable role for schools, and schools themselves are best placed to make staffing decisions to reflect their individual needs. It is up to head teachers and governors to decide who is required for the job and this includes how best to cover absences.
"The number and quality of teachers is at a record high, with over 1,000 more graduates training to teach secondary subjects now than a year ago. The overall teacher vacancy rate is 0.3% and has remained around or below 1% for the past 15 years."