Pupils at the school were left 'unprotected' the report said.
A damning report into the management of an East Yorkshire school says pupils were left "unprotected" for 13 years by senior staff.
Two teachers at Headlands School in Bridlington were convicted of having sex with female pupils in 2005.
Another teacher who then moved to a different school was also convicted of having sex with a teenage girl there.
East Riding of Yorkshire Council said guidelines for employing staff tightened up.
The former head teacher of Headlands School, Anthony Halford, has been heavily criticised in the report by East Riding Safeguarding Children Board.
And it has emerged that crown prosecutors had considered charging him with official misconduct in public office, but decided against the move.
The scandal came to light in October 2005 when teacher Ian Blott went to the headmaster and confessed to having sex with teenage pupils at the school.
In a subsequent investigation around a dozen teachers at Headlands School came under suspicion.
One of those, Stephen Edwards, was convicted of having sex with a pupil.
Another teacher, Terry Mann, who had moved to Withernsea School, was convicted of having sex with a girl there.
The report, carried out by East Riding of Yorkshire Council and Humberside Police, highlighted a number of concerns were raised by staff with the Headlands management about the behaviour of some teachers - but no action was taken.
Alison Waller, the Director of Children's Services at the council said lessons have been learned from the inquiry.
"I think it is important that teachers and head teachers are appointed by the governors of schools.
"As a local authority we do advise and we're very happy to be involved in it.
"But actually the decision around hiring and firing is with governors.
"What has moved on significantly since the time when these particular teachers were appointed is actually there are now new statutory requirements nationally to ensure that appropriate staff are appointed to work with all children - not just in schools.
"It gives the local authority far more powers of intervention when things are going wrong.
"We are in a different world now and legislation has caught up."