The schools watchdog faced calls today to highlight sexual abuse involving teachers in its reports after it was revealed parents were being kept in the dark.
A Channel 4 News investigation found Ofsted inspectors were routinely failing to mention instances where teaching staff had either been convicted or were awaiting trial for offences against pupils.
But the watchdog said individual cases of "inappropriate behaviour" were a matter for "the police and the relevant local children's services".
Channel 4 News looked at eight instances where Ofsted failed to highlight cases of sexual abuse.
At Headlands comprehensive in Bridlington, five members of staff were convicted over a five-year period. But there was no mention of the abuse in seven Ofsted reports in that time.
Police started investigating allegations made against a science teacher at the school in 2003.
The following year Ofsted inspectors reported child protection arrangements were "secure".
By 2008, three members of staff had been prosecuted for child sex offences.
Despite this, Ofsted's report in May of that year made no mention of the problem, adding that "procedures for the safeguarding of students meet national requirements".
Within months of that report, a female classroom assistant received a conditional discharge following a relationship with a pupil. Her replacement was later jailed for three years after embarking on an affair with a 15-year-old.
The mother of the girl told Channel 4 News: "I think if they had been regularly reporting on safeguarding issues and had been honest about what had happened in the past, then things would have been better for my daughter and maybe it wouldn't have happened."
Channel 4 News found other examples of child sex offences being missed off reports by Ofsted inspectors.
Barry Sheerman, who chaired the Commons schools select committee in the last parliament, told the programme he was "shocked" and "astonished" by the findings.
He told Channel 4 News: "We're been going through some pretty hard times with Ofsted at the moment.
"It's growing fast, it's growing to be a very big inspectorate and it's time, I think, it needs to be assessed very carefully by government, by the department, to assess if it's fit for purpose."
But in a statement, the watchdog said: "Ofsted has an important role in checking that schools are doing what they should to keep pupils safe.
"Our inspectors make sure that the right checks have been carried out on staff and that pupils know how to ask for help. Our inspections cannot vouch for the behaviour of every member of staff, but ensure that the school is taking the right action.
"We do not investigate or report on individual cases of inappropriate behaviour.
"These are rightly a matter for the police and the relevant local children's services.
"When we inspect, we consider fully any information relating to safeguarding, including information shared with us by the Independent Safeguarding Authority, and any such issues are considered as part of our inspection."