A family has complained that their son has been denied a place at the Moriah Jewish Day School nursery in Pinner, Harrow in September because the school miscalculated the distance from their home.
The boy's father, who did not wish to be named, said that other children who lived further away from the school had been placed higher than their son in the queue for 26 places.
Like other schools, Moriah gives priority to applicants who live closer to the school. But the father said that the school had failed to adhere to an admissions policy which states that the distance would be measured "as the crow flies".
He said that, according to Google's "as the crow flies" website, the family's home in Stanmore lay some 6.5 kilometres from the school. But the school calculated the distance to be nearly eight kilometres away.
"What is clear is that our son should have been offered a place," he wrote to Moriah.
"Children living in Bushey, Bushey Heath and Stanmore Hill are in front of us, either having been offered a place or are ahead of us on the waiting list."
But Moriah's head teacher, Reverend Alan Shaw, said: "For nursery admissions we have used a computerised mapping system to calculate the distance from applicants' homes to the school set up for us by an expert. The system calculates this distance which is stated to be 'as the crow flies' and we have applied this system for 11 years. We regret that we cannot accommodate all those seeking places."
The admissions policy explains that distance would be measured "in a straight line using a computerised mapping system based on ordnance survey data".
But Mr Shaw - who said there were three times as many applicants as nursery places - said that the term "as the crow flies" would be dropped from the entry policy for 2011.
Unlike with entry for reception class at primary school, parents do not have the right of appeal for nurseries.
This is not the only dispute over calculating distance for school entry to have broken out this year.
Hertfordshire Council admitted that it had made the wrong measurements in the case of six children who failed to find places at the Hertsmere Jewish Primary School nursery.