Besides the worry that, as a father, he was unlikely to be given custody, he also had to overcome the testimony of a court-appointed psychologist who favoured the child’s mother.

But Welber, 56, from Tampa, won the case. A comparison that showed the schools in his community were better for his son than those in his wife’s new town led to him being given custody. The issue of school quality is being raised more and more in custody disputes in the United States as parents become aware that there are vast disparities between schools, depending mainly on the economic state of the communities that run them.

“School quality has become a paramount concern in custody cases,” said Michael Pitts, an attorney and director of the Children’s Rights Council in Washington DC.

The strategy apparently took root by accident when an executive in a child custody dispute learned that his company rated local school systems to help its new employees choose a place to live. He used the information to stop his child’s mother frommoving to another state - and into an inferior school district.

Experts compare schools based on their courses, college preparation, test performance, expenditure per pupil and the number of students per teacher.

“A youngster spends more waking hours in school than he does with his parents, and the school can play a vital role in terms of college and university admission, in terms of employment opportunities, in terms of personal adjustment,” said William Bainbridge, founder of School Match, an Ohio consultancy that rates schools.

The phenomenon has grown so quickly that School Match last month made its rankings available directly to attorneys through a national computer database used for legal research.

In Welber’s case, a comparison showed schools in Florida were able to offer outdoor sports all-year round, while the school in the mother’s new town specialised in teaching the children of foreign executives and diplomats. Florida was “better fit” for the child, the judge decided.

Some go so far as to argue that school quality is as important an issue as a parent’s competency. “The compatibility of the parent is less important than school quality if the parent is never around to support the child,’’ Bainbridge said.

Carmen Ferrante, a New Jersey judge and president of the National Council of Family Court judges, said: “You shouldn’t decide custody cases on the wealth or poverty of one or the other parent. Just because somebody’s rich and can afford a better school doesn’t necessarily mean they’ll be a better parent.”