The official admissions body has made a fresh crackdown on schools offering automatic places to teachers' children.
Nine schools in Surrey were reported to the Office of the Schools Adjudicator by council officials for showing favouritism towards staff.
Many schools said the perk for teachers was necessary to overcome staff shortages, a problem that was exacerbated by poor public transport.
But the adjudicators, Andrew Baxter and Alan Parker, said it contravened the Government's code of practice on school admissions.
They said that teachers' children should not be given a place at the expense of local youngsters.
The ruling follows a warning by Philip Hunter, the chief adjudicator, in his annual report earlier this year, that prioritising teachers' children was akin to doctors fast-tracking their family into hospital.
Dr Hunter said he dealt with 26 complaints of staff favouritism last year.
In Surrey, the council complained about nine voluntary-aided and foundation schools, which can set their own admissions rules, after they refused to sign up to a county-wide admission policy adopted by all other schools.
A spokeswoman said that the schools - Burstow primary, Epsom and Ewell high, Fullbrook secondary, Holy Trinity juniors, St Nicholas primary, Woking high, Ewhurst infants, Tadworth primary and Yattendon secondary - were contacted by letter asking them to reconsider, but they failed to agree.
"It was felt that the criteria these schools were using were not fair," she said.
One school argued that the practice of giving places to teachers' children was a response to recruitment and retention problems, "particularly in view of the relatively poor public transport available to pupils and staff at the school".
But the adjudicators, who upheld or partially upheld all nine complaints, said that such a policy should be "subordinate to a higher priority relating to local families", in effect rendering it redundant.
David Hart, general secretary of the National Association of Head Teachers, said he was not aware that the policy was widespread in the state system, although some private schools offer teachers discounted fees for their children to attract the best candidates.
"I am sympathetic to schools if they are having problems recruiting and retaining teachers, but they are skating on thin ice by giving teachers preference over other parents who may live closer to the school," he said.