Sub-standard teachers should be removed from schools to make way for better colleagues, a key government education adviser has suggested.
Poorly performing teachers meant pupils suffered, Sir Cyril said
Sir Cyril Taylor said there were about 17,000 "poor" teachers in England.
They were unable to control classes and were damaging the education of about 400,000 children, he told the BBC.
But head teachers said it was sometimes difficult to recruit good staff, while teachers said their job was made harder by issues such as paperwork.
'Recruit fantastic teachers'
Sir Cyril, chairman of the Specialist Schools and Academies Trust, called on head teachers to be stronger in getting rid of poor performers.
He said: "We've got 400,000 of our children attending low-attaining schools; 75,000 leave schools at 16 with hardly any qualifications at all; five million adults are functionally illiterate.
"That's a serious problem.
"The head teacher that is good can take the necessary action, you get the wrong people off the bus and get the right people on the bus in the right seats.
"That means if you have weak heads of department you ask them to move on and you go out and recruit fantastic teachers."
The government says that ultimately head teachers are responsible for the quality of teaching and they should take action against poor performers.
But head teachers' unions say recruitment can be difficult, especially with shortages in maths and science.
National Association of Head Teachers deputy head Clarissa Williams said: "Faced with a crisis in recruitment, some head teachers may feel that it's better to have anyone in front of a class than no-one, simply because they have a responsibility to have that class taught by a qualified teachers.
"In terms of quality of that person, hopefully they will be able to do it, but there is no guarantee."
And teachers say the job is becoming more difficult.
Teacher Frances Gilbert said problems they had to deal with included parents unwilling to accept the disciplining of their child, government paperwork, and head teachers who would not back them up.
"It all amounts to a toxic brew which makes our teachers some of the most unhappy in the whole of western Europe," he said.
The head of education at the union NUT, John Bangs, said he disagreed with Sir Cyril's assertion.
"I cannot understand where he's got those figures from.
"We have the best teaching force we've had for years and years.
"Our experience at the NUT is that people who are beginning to feel burned out, leave. That's the big problem."
In a profession of 500,000 there will always be teachers who have problems in the classroom, but Mr Bangs said there were ways of dealing with them, such as "capability procedures" and inspections.
Former chief schools inspector Chris Woodhead said poor performing teachers should be monitored and offered support, but if there was no improvement after about six months then they should be sacked.
"Obvious" weaknesses, such as not knowing enough about their subject or being unable to keep control of a class, would be grounds for dismissal, he added.
But he said teaching was a stressful job with low pay and difficulties in recruiting - all issues which the government needed to address.
He stressed: "Incompetence is unacceptable [and] the immediate responsibility is the head teacher's, but do not turn the spotlight away from the government because the government is ultimately responsible for the problem."