Cummins points out that English-language instruction does not merely develop English language skills, but a foundational academic intelligence, allowing for wider-ranging acquisition of knowledge. This is, of course, a two-way street. Instruction of the core curriculum, in Mandarin or Spanish does not merely develop Mandarin or Spanish language skills, but, rather, an underlying scholastic aptitude, applicable in either a native or acquired language.
Let’s say your 4th grader were taught a lesson about the Battle of Gettysburg in Mandarin or Spanish. If the lesson were focused on that battle's significance to the American Civil War vs. the memorization of names and dates, the student would be able to meaningfully answer questions on a test administered in English. Language would have only been the vehicle by which a foundational lesson was delivered, and the true takeaway would be the content learned.
This is reflected by our results. When administered the ERB, HWIS Grade 4 students—who receive instruction in the English language for only 20% of the day for the first three years of their elementary education—outperform students from Gifted & Talented (G&T) public schools and independent schools nationwide, by an average of 15.8 points.