Creative arts subjects are being cut back in many secondary schools in England, a BBC survey suggests.
More than 1,200 schools responded - over 40% of secondary schools.
Of the schools that responded, nine in every 10 said they had cut back on lesson time, staff or facilities in at least one creative arts subject.
But Ofsted chief Amanda Spielman said academic subjects were the best route to higher-level study, particularly for working-class children.
However, schools told the BBC that the increased emphasis on core academic subjects, together with funding pressures, were the most common reasons for cutting back on resources for creative subjects.
The data provides an up-to-date snapshot of decisions being made in secondary schools.
The findings suggest music, art and drama, as well as design and technology are all being squeezed.
Of the schools responding, four in 10 were spending less money on facilities, more than three out of 10 had reduced timetabled lessons, and some reported having fewer specialist staff.
In both art and music, one out of 10 schools said it was increasingly relying on voluntary donations by parents.
Extra-curricular clubs were also being cut back in a similar proportion of schools responding.
Jez Bennett, a musician and head teacher of Elizabeth Woodville school, in Northamptonshire, said: "I've had to make some decisions about whether I can afford to run certain classes, and I know that there are schools that have cut GCSEs in art, music, drama, photography."
One of the hard decisions was to cut subsidies for instrumental music lessons, with the cost passed to parents.
And the school no longer teaches dance as a separate subject.
Mr Bennett said these subjects taught a wide range of skills much in demand from employers, particularly "collaboration, creativity, self-expression and control".
Research from the Education Policy Institute has shown a decline in the proportion of pupils taking at least one arts subject at GCSE level.
In 2016 it reached 53.5%, the lowest level for a decade.
The schools responding to the BBC suggested this trend that could continue, with three in 10 saying they feared they would have to drop at least one creative subject at GCSE.
John Kampfner, from the Creative Industries Federation, said it was worrying that some schools were reporting that art subjects were now seen as softer options.
"Arts provision should also be seen as a core subject," he said.
"There's nothing soft about subjects that create the talent that creates the fastest growing sector of our economy."
A Department for Education spokeswoman said that between 2016 and 2020 the government will have spent £400m on arts and music education.
"Since 2011, the proportion of pupils in state funded schools taking at least one arts subject has increased."
The spokeswoman added that in council schools music is a compulsory subject up to Year 9 while "academies are required to provide a broad and balanced curriculum, which Ofsted consider in their inspections".
Amanda Spielman, Ofsted's chief inspector of schools for England, said she supported the shift back towards traditional academic subjects at GCSE, as these offered the best chance of progress to higher-level study.
"The worst thing that can happen to a working-class child is they don't get the full education to 16 that leaves them with options that could take them to university or vocational education," said Ms Spielman.
But she added Ofsted expected a broad education, including the arts, to be available in the early part of secondary school, arguing that schools should "embrace creative subjects" through extra activities such as plays, art clubs and orchestras.