A letter was sent out this week by Northamptonshire County Council to all parents and guardians of prospective pupils at Unity College to inform them that there is a proposal for the school to change its status.
However, for some parents, this wou
ld have been the first they have heard about the academy proposals since they visited the school at the end of last year.
Under the academy plans, current headteacher Margaret Gwynne would be replaced with Vanessa Ray, former deputy head of Northampton School for Boys.
Hilary Scott, whose eldest son has been offered a place at Unity College in September, said: "It is a like a breach of the Trades Descriptions Act when the thing you have bought is completely different when it arrives."
The uncertainty of the future of the school also seems to have put off some parents with new statistics on Tuesday showing that Unity College still had 61 places left to fill for this September, the highest figure of any of the schools in the town.
John Henry, a member of the Save Unity College group, said: "It was so obvious that this was going to happen because of all the uncertainty around the school and all the objections against the academy plans. Parents have voted with their feet.
"A lot of parents have chosen the school because it had a certain headteacher and it was doing quite well and things seem to be pointing in the right direction but they have basically been duped."
A spokesman for Northamptonshire County Council said: "Unity College is currently in special measures and any family whose child has been allocated a place would rightly expect that significant steps would be taken to improve the school's performance.
"There has not yet been a decision taken on whether the school will become an academy.
"The Government will rule on that in April.
"At this stage, we are in the middle of the statutory consultation into whether or not the council should close the school.
"Any pupil or parent who has been informed this week that Unity College will be their school from September is welcome to take part in the consultation and make their views known to us. That will ensure our cabinet can take their thoughts into account when the time comes to make a decision."
The county council cabinet will meet on April 14 to make the final decision on the future of the school.