Schools are using unqualified teachers to cover lessons and prepare pupils for exams, according to a new poll.
It suggests that classroom assistants and cover supervisors are among those being asked to take the place of teachers .
The survey of more than 2,000 teachers in England and Wales, conducted by the NASUWT union, found that more than half (58.7%) said unqualified staff are being used as teachers in their school.
Of these, around three in four (73.8%) said that these unqualified individuals are preparing lessons, 97% said that they teach lessons, and around half (50.8%) said these staff members are preparing pupils for tests and exams.
More than eight in ten (84.6%) of those questioned said that their school regularly uses unqualified staff as teachers.
The poll also asked teachers which roles these unqualified staff members held, and around 17% said that they were individuals on courses to gain qualified teacher status. Others said that these individuals included cover supervisors, higher learning teaching assistants, other teaching assistants and learning mentors.
NASUWT general secretary Chris Keates said: "Parents and the public should be deeply concerned at the results of this survey. Now when a parent sends their child to school they have no idea who is teaching them. Unqualified staff who are not being given the appropriate training, support and remuneration for their responsibilities are also being exploited."
She added: "If any suggestion was made that unqualified doctors were let loose on patients there would be public outrage. Why should our children and young people, the future of this country, be treated with any less concern?"
A Department for Education spokeswoman said: "It is simply not true to claim that this is about depressing costs. This is about raising standards. Independent schools and free schools can already hire brilliant people who do not have Qualified Teacher Status (QTS).
"We have extended this flexibility to all academies so more schools can hire great linguists, computer scientists, engineers and other specialists who have not worked in state schools before. We expect the vast majority of teachers will continue to have QTS. This additional flexibility will help schools improve faster, and give head teachers the freedom to hire the person best suited to their school."