San Francisco had to drop an earlier system based on racial quotas

The initiative in San Francisco will use a "diversity index" which will attempt to ensure that some less well off pupils have access to places in the most successful schools, regardless of where they live.

This scheme is based on family income and whether families are English speaking and will allocate places in a way that creates a mix of backgrounds.

It is expected that parents in the city will be receiving details of which school their children will attend this week.

Racial division

Until 1999, San Francisco had operated a scheme which used ethnicity as a factor in attempts to integrate pupils.

This had limited the proportions of ethnic groups in any individual school - with no more than 45% of pupils to be drawn from a single racial group.

But this was withdrawn after a court ruling against this policy.

Research published last year by Harvard University revealed a picture of growing educational segregation across the United States.

Between 1988 and 1998, the number of black pupils in schools where a majority of pupils were white decreased from 43.5% to 32.7%.

It found that 70% of black pupils attended schools in which a majority of pupils were black.

And that white pupils on average attended schools where 80% of pupils were white.

This reverses a trend from the 1950s to the 1970s which had promoted integration, following the abolition of segregated education.