The number of suspensions at Movilla High School, in Newtownards, County Down, was revealed in the latest report from school inspectors.
Its problems were first highlighted two years ago, when inspectors said its quality of education was "inadequate".
The latest inspection has found some improvements, but not in exam results.
In fact, the percentage of pupils who attained five or more GCSEs (or equivalent qualifications) at grade C or above has dropped from 23.6% at the time of the original inspection to 18.4%.
The number of pupils enrolled at the school has also dropped to 215 and Movilla has been without a permanent head teacher since July, when Caroline Karayiannis left her post.
In a statement to the Belfast Telegraph newspaper, the school's interim principal Ian Bell said: "The board of governors and management of Movilla High School acknowledge the findings of the ETI (Education and Training Inspectorate) follow-up report, and are encouraged by their endorsement of the positive changes made in the school from September 2015."
When contacted by the BBC, Mr Bell would not comment on the number of suspensions or add to his earlier statement.
The 440 suspensions at Movilla accounted for 12% of the total number of suspensions across all schools in Northern Ireland in the 2014/15 academic year, which stood at 3,647.
The statistics include repeat offenders as pupils can be suspended multiple times in a year.
Movilla High School was placed in "formal intervention" in January 2014 -  a process in which schools with unsatisfactory educational records are offered extra support to raise their standards.
Since then it has been the subject of a series of follow-up visits from ETI inspectors, the most recent in November 2015.
After their latest visit, inspectors said Movilla High School has been "adversely affected by a lack of strategic leadership, strained relationships at various levels and several long-term illnesses in key curriculum areas".
It said the school's problems were "compounded by a deteriorating system for the pastoral care and behaviour management of the pupils, as evidenced by the 440 recorded suspension incidents during 2014-15".
Although half of the lessons observed during the follow-up inspection were "good or better", the inspectors said they witnessed some classes being "disrupted by low-level misbehaviour by a small number of pupils, which needs to be managed to better effect".
However, the report also said that in the first three months of this academic year, the school's "senior leadership team and the staff have worked collegially to put in place measures to promote positive behaviour by the pupils".
It also said that relationships "between staff at all levels have improved".

The male hedgehog, who had inflated to twice its size, was found wandering around in circles by a member of the public in Toll Bar, Doncaster.
The unnamed animal was diagnosed with the rare "balloon syndrome", caused by gas collecting under the skin.
He was taken to a RSPCA centre in Cheshire where a needle was inserted to vent the trapped air.
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Bev Panto, head vet at the RSPCA's Stapeley Grange centre, said it was a very unusual syndrome.
"In my career I have seen three or four of these cases and they are very strange every time and quite shocking," she said.
"When you first see them they appear to be very big hedgehogs but when you pick them up they feel so light because they are mostly air."
She said the condition only occurs in hedgehogs and was due to their ability to curl up, meaning they have a lot of space under the skin.
In some circumstances air can get trapped under the skin due to an injury or trauma.
"They literally blow up like a balloon," she said.
"The first thing to do is to just pop them. To pop a needle in and drain all that air out."
Ms Panto said the hedgehog was eating well and staff were hopeful of a full recovery.
"It is certainly not out of the woods yet so it's fingers crossed," she added.
A school suspended pupils 440 times in one academic year, despite the fact that only 353 students were enrolled at the school during that period.
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A hedgehog who had "blown up like a beach ball" is said to be doing well after a vet "popped" him with a needle.