Dual language program is not a codeword for instruction in Spanish for Spanish speakers and English for English speakers. These programs teach some subjects in Spanish and some in English for the students in their classes. Spanish speakers receive half of their classes in English and English speakers receive half of their classes in Spanish. The goal is to graduate students that are fluent in two languages instead of just one.
Two of my kids went through a dual language program, and they were great. The program was modeled by the European schools that teach their students their local language and English as well. You might want to do some research before you make assumptions.