53 students have already left Al-Madinah school in Derby ahead of the closure of its secondary classes.
The figures have emerged in the latest Ofsted inspection report following a monitoring visit last month.
The Department for Education announced that secondary provision at the Muslim free school would end when the current academic year finishes in July.
Since the decision in January, the school and the city council have been working to find places for its pupils at other secondary schools in Derby.
Ofsted says there were 140 secondary students at the time of its previous monitoring inspection in November. There are now 87.
The controversial Al-Madinah free school in Derby is making "reasonable progress", according to Ofsted inspectors who carried out a monitoring visit last month.
The school hit the headlines last year when there were numerous complaints from staff and teaching unions about the way it was being run.
It was placed into special measures and described as "dysfunctional" by Ofsted. Education minister Lord Nash subsequently decided to close the secondary school at the end of this academic year.
Since then, the original trustees have been replaced by a new board, and the school has been supported by Greenwood Dale Foundation Trust in making improvements.