UNIVERSITY PARK, Pa. -- Mexican American mothers' formal immigration status affects the educational achievement of their children and even their grandchildren, according to a study written by Penn State and University of California, Irvine, sociologists and released by the US2010 Project at Brown University.

Based on a large-scale survey of second-generation Mexican young adults in Los Angeles, the study finds that those whose mothers were authorized immigrants or U.S. citizens averaged more than two years more schooling than those whose mothers entered the country illegally. The researchers estimate that more than a third of the education gap between third-generation Mexicans and native whites is attributable to the legacy effects of grandparents' unauthorized status.

"The fact that Mexican-origin children appear to fall behind most of the rest of the population in terms of educational attainment has long been a concern of researchers and policy-makers," said James Bachmeier, research associate, Population Research Institute, Penn State. "This report indicates that this derives in large part from the fact that many of these children are raised in families in which one or both parents lack legal status."

This study and future studies may help guide the national debate on immigration reform, said Bachmeier, who worked with Jennifer Van Hook, director of Population Research Institute and professor of sociology and demography, and Mark Leach, former assistant professor of rural sociology and demography, both of Penn State.

"The extent to which parental legal status shapes the opportunities of U.S.-born children warrants more attention in the future, especially as Congress discusses comprehensive immigration reform," said Bachmeier.

According to the study, legalization may help the children and even grandchildren of immigrants increase their educational attainment.

"The implication of our findings is that clear pathways to legalization can boost Mexican American educational attainment even as late as the third generation," said Frank D. Bean, professor of sociology at the University of California, Irvine. "Legislation providing the possibility of entry into full societal membership helps not only the immigrants themselves but also their children and their children's children."

The study looked closely at the trajectories of parental immigration status. In 10 percent of cases, the mother was U.S.-born but married to an immigrant spouse, and about 44 percent entered the country legally. It is in comparison to the children of these mothers that the researchers found a disadvantage for those whose mothers were unauthorized immigrants -- about one third of mothers.

"There are nearly 4 million children of Mexican immigrants living in this country, most of them born here," said Bean. "At present, with few pathways for their parents' legalization, they live too long in the shadows. Because America's future labor force depends so heavily on the children of immigrants, we all have a stake in their progress."

Susan K. Brown, associate professor of sociology, University of California, Irvine, also worked on the report.

Funded by the Russell Sage Foundation and Brown University, the US 2010 research project examines changes in American society in the recent past.