A Derbyshire school will be forced to give priority to children in care instead of children of staff after it tried to change its rules.
Ecclesbourne School in Duffield, is one of the county's most over subscribed.
The school wanted to change its admissions policy rules when it did not have enough places.
The Schools Adjudicator said children in public care should be the top priority and children of staff should not be given preference.
The Office of the Schools Adjudicator decides on issues which cannot be resolved locally.
The city council had accused the school of discrimating against less well off parents.