Ofsted chief Sir Michael Wilshaw has suggested closer scrutiny of schools may be needed as he confirmed the watchdog has visited other towns and cities in the wake of the alleged "Trojan horse" takeover plot in Birmingham.
The watchdog has visited schools in areas including Bradford and Luton due to concerns about how they are being run, he told the Commons education select committee.
Sir Michael also told the cross-party group of MPs that several headteachers in Birmingham believed that there had been a "planned and orchestrated" campaign to take over schools in the city.
The committee is holding evidence sessions on extremism in schools following allegations of a plot by hardline Muslims to take over a number of Birmingham schools.
Last month Ofsted issued a damning verdict on the running of a number of schools in Birmingham.
Five schools in the city were placed in special measures after a series of inspections in the wake of the "Trojan Horse" allegations.
The Ofsted chief was asked if there was an issue elsewhere in the country with governors seeing their role as running a school rather than setting policy.
"We are looking at other schools where this might be happening," he said. "We've certainly been to schools in Bradford and Luton."
He said that where Ofsted receives information about concerns, they are conducting unannounced inspections.
He suggested that there was a "wider issue" about how schools are governed, revealing that Ofsted has been looking at around 20 schools across England that have been downgraded from outstanding to inadequate due to "failings in governance".
"Where we see serious problems with governance then that affects our decision and our judgments, and we've about 20 schools which have been downgraded from outstanding to inadequate due to failings in governance, and serious failings in governance."
He later told the committee that there needs to be more professional governors, saying there has been a reliance on "amateurish governance to do a professional job".
Sir Michael said that several headteachers in Birmingham believed that there had been organised infiltration of the governing bodies of schools by Muslim hardliners.
"The headteachers I spoke to believed there was orchestration and manipulation. I spoke to about eight or nine headteachers and they believe it was planned and orchestrated.
"They believed people got together and decided which schools to target.
"They believed that often governing body meetings couldn't take place in the normal manner because governors were determined to get their way."
He suggested that there may need to be a change in the law to allow outstanding schools to be inspected more often.
"We do re-inspect outstanding schools where there is a dip in performance and where our risk assessment process triggers an inspection," Sir Michael said.
"I think we need to review this.
"Possibly there needs to be a change in legislation to allow us to inspect outstanding schools on a regular basis in a way that we intend to inspect good schools."
Plans are in already place to inspect "good" schools more often, but Sir Michael said he would like to see inspectors going into those schools every three years to make sure that they still meet the assessment.
"Even within these shorter inspection schedules schools can slip. There is a big debate to be had about how increasingly autonomous schools are going to have effective oversight."
He said he would like to see inspectors "in schools every three years to check that they are still good schools".
The committee heard that new regional commissioners face "a very, very, very big challenge" in oversight of large numbers of schools, and that instead clusters could be created where "an outstanding leader" monitors the other schools in the same group.
Sir Michael said: "The future could be Ofsted inspects the cluster rather than individual institutions, especially if our budget is cut even more."
The Birmingham schools declared failing and placed in special measures following Ofsted's inspections had declined rapidly, the committee was told.
A number of schools visited had previously been rated as good or better.
Sir Michael was asked by the cross-party groups of MPs if it was possible that inspectors had missed signs of problems during previous inspections. In reply, the Ofsted boss said the inspectors are usually in schools for around a day and a half.
"It's possible to miss these issues," he said.
"Particularly if headteachers are frightened, if school leaders are frightened, if teachers are frightened to speak out because of fear for their jobs, fear they won't be promoted."
He added that in these situations it is "difficult" to pick things up.
Sir Michael was later asked if there are "significant shortcomings" in Ofsted inspections, and replied that he refuted this.
The schools involved had declined rapidly, he said, and one of the main reasons for this was headteachers leaving, which creates instability. This can happen in weeks, Sir Michael told the committee, and is why problems may not have been picked up during the first inspections.