Massive illegal immigration from Mexico has increased net government revenues in California and has not cut into the earnings of American citizens here, but advances in public education may be necessary to prevent future problems, the Rand Corp. reported last week.

The 18-month study sponsored by the California Roundtable, a business assocation, cited Census data showing fewer than 5 percent of all Mexican immigrants, legal and illegal, in the state receiving public assistance, compared with 12 percent of all adults statewide.

Its authors, demographer Kevin McCarthy and economist Robert Valdez, said that Mexican immigrants appear to pay more in taxes than they receive in government services, "with the notable exception of educational services."

The study, which focused on the immigrants' impact on the state, appeared more optimistic than a study recently released in Washington by the National Council of La Raza. That report said Latinos are the least educated and lowest paid ethnic group in the country, with unemployment rates much higher than official figures indicate.

But, like the La Raza report, the Rand study called for special efforts to increase educational opportunities for Latinos. The study concluded that Mexican immigrants here, on balance, do not take jobs from Anglos or blacks, but do displace other Latinos. The Rand researchers said that the state should "accelerate the educational advancement of future native-born Latinos so that they will be able to qualify for jobs in the state's white-collar sector, where the growth in the economy is going to occur."

"Contrary to what many believe," McCarthy and Valdez reported, "the integration process among Mexican immigrants and their offspring is very similar to that of European immigrants" in the last century. Ninety percent of the first generation born here speak good English, the researchers found, and most of the second generation speak only English.

This is one of the benefits that balances the high cost of educating growing numbers of immigrant children, the study said. Latino progress seems slow only in comparison to Asians, who arrive better educated than any immigrants in U.S. history and whose children "move into higher education and white-collar jobs one generation faster than Latinos," the study said.

The study said that 45 percent of Latinos in California, who total at least one-fifth of the state's population, are immigrants or the children of immigrants.