The two issues were the most pressing concerns for almost two-thirds of heads, followed by pupil behaviour, a report for the National Foundation for Educational Research found.
In the first Annual Survey of Trends among secondary school leaders, nine out of ten of the 1,224 who took part, said they were overworked, and more than 80 per cent said they worried about teachers' workload.
A similar study of primary heads has been carried out for the past 11 years.
Given a hypothetical budget increase of 5 per cent, almost six out of ten heads said they would employ more classroom and welfare assistants, while just over half would hire more secretarial staff.
Four out of ten said they would employ more teaching staff, while 30 per cent would improve school buildings.
Most heads, almost 60 per cent, expected that the Government's planned three-year budgetary cycle for schools would have a positive impact, making it easier to plan ahead.
However, just over a fifth believed the changes would have no impact and 4 per cent feared they would have a negative impact, with schools not getting enough money to safeguard against falling rolls.
Heads were also positive about new shorter school inspections, with 64 per cent believing that they would reduce "pre-inspection hysteria".
Just over 30 per cent welcomed new co-ordinated admissions procedures, though a fifth feared local education authorities might mismanage the process.
A lack of cash was cited as the main obstacle to developing their schools into "extended schools" offering a range of community services and open for longer hours, which will.
However, 90 per cent of heads said that their schools already offered additional services, and more than two-thirds planned to expand the range of facilities offered to families and the local community.
John Dunford, general secretary of the Association of School and College Leaders, said heads wanted "more sustainable education policies, with fewer initiatives and less emphasis on short-term results".
He said: "Budgets remain a major issue in some parts of the country.
Although teacher recruitment has improved in the last two years, the government cannot afford to let up on recruitment initiatives."
Why be a head? Opinion 23 www.nfer.ac.uk