Parents say they are considering removing their children from a school rated "outstanding" amid concerns over bullying.
The Colne, in Brightlingsea, is part of the Thrive Partnership Academy Trust.
One parent told the BBC his daughter had been "horrendously" bullied and had last week called him from the school toilets in tears.
The school said it "takes any allegation of bullying extremely seriously".
In a statement it said: "[The school] takes appropriate action to quickly deal with any issue brought to our attention.
"We cannot comment on an individual case, but have an open door policy for students or their parents to raise any concerns they have with us."
When the Colne was inspected in 2013 it was judged "outstanding" and described as an institution at which pupils felt "very safe" and where bullying, when it "very occasionally" occurred, was "swiftly dealt with".
Minutes of governing body meetings obtained by the BBC show how in February governors were told the school had seen an increase in student exclusions and a "rise in extreme behaviour".
There was also a "perception that the school had a bullying problem" and that while students were "aware of how to report bullying, many did not engage because they felt that no action was taken".
An Ofsted spokesman said an unannounced two-day inspection was carried out earlier this month after it was alerted to "ongoing parental concerns".
One parent said his daughter had experienced "nothing but trouble" since joining the school.
He said she had been "pushed around by three or four" older pupils and had been repeatedly called names.
He is now considering removing his daughter from the school.
Another parent described how she had already taken her daughter out of the school after receiving a call from her while she cowered in the school toilets.
"It was really bad, you could hear them all jeering her," the mother said.
"We got in the car and said that was it, we are taking her out of school."
Both parents say they were never invited in for a meeting at the school.
Essex Police said it was waiting to speak with the Colne about a "recent event", though details of the incident remain unclear.
A school spokesman previously told the BBC: "We constantly strive to engage with our parents over issues they raise.
"Unfortunately, there are some occasions when issues raised are not always resolved to parental satisfaction.
"In these instances, we always direct parents to follow our Complaints Policy and Procedure where they can be fully investigated."
The full story and reaction will be broadcast on BBC Essex's Breakfast with Ben and Sonia show from 06:00 BST on Friday.