The controversial measure, known as Proposition 227, is being put to a ballot on Tuesday. It would have the greatest impact on the quarter of pupils in California who have limited English - about 1.4 million children, overwhelmingly Spanish-speaking.

Those who have difficulty with English would undertake a one-year 'immersion programme' in the language before going into ordinary classes.

It would overturn almost three decades of bilingual education, in which pupils were taught first in their native languages, with English being introduced in later years.

The proposition is one of nine special measures being put to a vote as part of the state elections. Recent opinion polls suggested about 60% of people were in favour.

It is the initiative of a millionaire Republican businessman, Ron Unz, who has no children or background in education. He says that the failure of California's bilingual education programme has resulted in the segregation of students by language.

Advocates of Proposition 227 argue that for most of California's non-English speaking students, bilingual education actually means Spanish-only education for the first four to seven years of school.

High dropout rates

They say that, last year, fewer than 7% of limited-English students learned enough English to be moved into mainstream classes. The main 'victims', as they put it, were Latino immigrant children, with the lowest test scores and the highest dropout rates of any immigrant group.

It is also argued that with 140 languages being spoken by California's schoolchildren, teaching any group in their native language before teaching them English is educationally and fiscally impossible.

Against that, opponents say Proposition 227 imposes one untested method for teaching English on every local school district in California, and in effect outlaws the most successful local ways of teaching English.

The California School Boards Association opposes the measure, as does the state's parent-teacher association, which complains that it takes away parents' right to choose what is best for their children.

Government opposed

The opponents accept that children in California must learn English. They argue that that is happening anyway. They acknowledge that there have been failures, but say that local control is the way to remedy things.

The Clinton administration is against the proposition. The Education Secretary, Richard Riley, said it would "lead to fewer children learning English and many children falling further behind in their studies."

Instead, he said, schools should limit children's participation in bilingual programs.

"I propose setting a three-year goal to make sure that a child is learning English," Riley said in April.