And policies such as California's Proposition 227 that assume acquisition is possible in as little time as one year are "wildly unrealistic," the study says.
The study, "How Long Does It Take English Learners to Attain Proficiency," was done by Stanford University researchers Kenji Hakuta, Yuko Goto Butler and Daria Witt, who studied students in two San Francisco-area school districts and interpreted data gathered in Canada by other investigators.
"The clear conclusion emerging from these data," the researchers wrote, "is that even in two California districts that are considered the most successful in teaching English to (limited English proficient) students, oral proficiency takes three to five years to develop and academic English proficiency can take four to seven years."
Under such circumstances, the report says, it makes more sense to set aside the eight years of elementary and junior high school as a reasonable time frame for students to gain English proficiency.
"What this study would suggest is you need a long-term view and a long-term set of expectations about learning," Hakuta said.
Even with English acquisition stretched over an eight-year period, it may be necessary to initiate special summer and after-school programs to bring such students to the level of their English-only peers, whose own language skills continue to grow and improve during these formative years, the report said. Without such intervention, the performance gap between English learners and native English speakers continues to widen, as the report documents.
All the while, educators need to take steps to keep students moving ahead on schedule in a balanced curriculum that addresses all their scholastic needs.
Hakuta said that could happen through bilingual education, but that educators should strive to find whatever means is most successful.
The report also suggested that as in other academic pursuits students in more affluent schools and school districts do better at acquiring English and keeping up in other classes than do students in poorer areas.
Russell Rumberger, director of the LMRI, said the study is significant ground work in the effort to make language minority students literate in English.
"It is really important to know how long we should expect it take these students to acquire English and to discover the best ways to learn English,"Rumberger said. "This is a very timely issue that is pertinent to the many reform efforts now being undertaken in California."