Teacher shortages in English schools are growing, with the government missing its own recruitment targets for the last four years in a row, the public spending watchdog has found.
While the overall number of teachers has gone up, the National Audit Office said shortages were also growing, with poorer areas particularly badly hit.
According to the NAO, while the overall number of teachers has "kept pace with changing pupil numbers", shortages are on the rise, and the Department for Education has a "weak understanding" of the scale of local gaps and how to resolve them.
"The NAO’s own research suggests problems in poorer areas, with some 54% of leaders in schools with large proportions of disadvantaged pupils saying attracting and keeping good teachers was a major problem compared with 33% of leaders in other schools," the report said.
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Secondary school teacher training places were said to be "particularly difficult to fill", with the department struggling to recruit enough trainees "in the majority of secondary subjects".
It means that more and more classes at secondary level are being taught by teachers who do not have a graduate qualification in the subject. In a particularly stark example, some 28% of physics lessons are being taught by teachers whose highest physics qualification is an A-Level.
While the NAO says the DfE and its executive agency, the National College for Teaching and Learning, "have grown school-led training" – with the number of providers rising from 56 to 155 in the past five years – it warns that potential applicants "do not yet have good enough information to make informed choices about where to train", with the range of training routes seen by some as "confusing".
"Training a sufficient number of new teachers of the right quality is key to the success of all the money spent on England’s schools," said NAO head Amyas Morse.
"The department, however, has missed its recruitment targets for the last four years and there are signs that teacher shortages are growing. Until the department meets its targets and can show how its approach is improving trainee recruitment, quality and retention, we cannot conclude that the arrangements for training new teachers are value for money.”
The head of the National Union of Teachers, Christine Blower, said the situation would "only get worse" unless ministers address issues such as "pay, workload and excessive accountability".
But a Department for Education spokeswoman said more people were entering the profession than leaving and blamed the unions themselves for "talking down teaching as a profession".
"The reality on the ground couldn't be more different, with the quality of education in this country having been transformed by the most highly qualified teaching workforce in history, resulting in 1.4 million more pupils being taught in good and outstanding schools compared with five years ago," the spokeswoman added.