The ruling, from the admissions adjudicator, reduces selection from 50 to 35 per cent of the intake at the schools in and around Watford, Hertfordshire.
The aim is to increase the number of places for local children, some of whom attend schools that are more than five miles from their homes. But one headteacher admitted the changes would not radically change the pattern of local admissions.
Other rulings issued this week by adjudicators will affect admissions policies at schools in Croydon, south London, Surrey and Derbyshire.
The Watford area has a history of admission problems. Education Secretary David Blunkett imposed a county-wide admissions system last year, after hundreds of children in the town were left without places following two admissions rounds. Most were eventually found schools, but some faced long journeys out of the area.
This year, the new system ensured that every child was offered a place. A Hertfordshire spokeswoman said 92 per cent were offered one of the three schools chosen by their parents.
Around 16 per cent of available places in Watford were offered to children from outside Hertfordshire.
Adjudicator Professor David Newton's decision has been welcomed by some local heads, who were concerned that a bigger cut in selection would affect the character of their schools. They argue that the geographical clustering of schools in the area makes admissions criteria based on pupils attending their nearest school impractical.
Hugh Forsyth is head of Rickmansworth school - one of the five schools affected by the ruling. He said: "It will produce more places across the area for children to attend their closest school if they want, but it does deny access to those children who live further away. This will help, but it won't radically change the pattern of admissions in the area.
"I would have been very unhappy if the selection element had been removed altogether, for the reason that the alternative - mainly geographical - would not work in this area given the dispersion of schools."
In Derbyshire, adjudicator Louise Kidd upheld objections to Netherthorpe school, in Chesterfield, increasing its intake. Rosebury school in Epsom has been ordered to reduce selection from 30 to 10 per cent by adjudicator Peter Neafsey.
In Croydon, Gordon Hainsworth has restricted admissions criteria, giving priority to children with "family links" to a school, to siblings only, and directing that two primary schools should be named as feeder schools to Edenham school.
He also threw out a rule at Riddlesdown high school, which required parents to sign up to its code of conduct.
But he did not object to partial selection (15 per cent) at Riddlesdown and two other schools (Shirley Foundation and Archbishop Lanfranc Foundation), on the grounds that there was no evidence the arrangements were denying local pupils admission.