A new study has found significant reading gains for students enrolled in a dual-language immersion program.

Dual-language immersion students in Portland, Oregon, outperformed their peers in English-reading skills by almost a full school year by the end of middle school, finds a new study by the Rand Corporation, the American Councils for International Education and Portland Public Schools.

Researchers, led by Jennifer L. Steele of American University, tracked the reading, math and science scores of about 1,600 students who were randomly assigned to kindergarten between 2004 and 2010 in the dual-language immersion programs in Spanish, Japanese, Mandarin Chinese and Russian with other students who had applied for the program but had not been selected in the lottery.

Students in the immersion programs scored significantly higher on the Oregon state tests in reading — the equivalent of seven months of learning by the end of 5th grade and nine months by 8th grade. Native Spanish speakers reaped the greatest benefit in reading from participation in the dual-language program. In addition, English language learners in dual-language immersion were three percentage points less likely to still be classified as needing English language instruction by 6th grade than those who were not in the program.

No benefits were realized in math or science from participation in dual-language immersion, but no negative effect was detected either.

Portland’s dual-language program consists of two types of classes — those in which half of the students are native English speakers and the other half are native speakers of the language being taught and classes in which most students in the classroom are new to the second language.