Parrish et. al. provided two analyses: In a "quasi-longitudinal" study they analyzed SAT9 results for English learners who were in grade 2 in 1998 and in grade 5 in 2001. This is considered only "quasi-longitudinal" because the two groups were not identical, because of transiency. There was practically no difference in gains between those in schools that kept bilingual education and those in schools that dropped bilingual education. In schools that kept bilingual education, the gain was from 537 to 621, 84 points. In those that dropped bilingual education, the gain was from 540 to 623, 83 points.

A second analysis was cross-sectional. In 1998, fifth graders in bilingual education scored 613, and fifth graders in schools that were about to drop bilingual education scored 614. In 2001, the fifth grade scores were 621 for schools that kept bilingual education and 623 for schools that did not.

Not all English immersion was pure English immersion, however. Parrish et. al. reported that for 75 districts that said they used "structured English immersion," 68% reported that teachers used the child's first language "occasionally or frequently" for academic content instruction, 88% used it occasionally or frequently for "preview-review," that is, presenting information first in the primary language as a preview, and 48% reported that they used instructional aides who spoke the first language occasionally or frequently. Their comparison, thus, appears to have been between bilingual programs and programs that used aspects of bilingual education.

3