What are the features of the most effective two way immersion programs? They last at least six years. Half of students are English speakers and half speak the target language (usually Spanish). The languages are taught separately by person, place, subject, and/or time. All of the above.

The most effective two-way immersion (TWI) programs typically incorporate **all of the features** you've listed: 1. **Duration of at Least Six Years:** Longer program durations allow students to achieve higher proficiency levels in both languages, fostering bilingualism and biliteracy. 2. **Balanced Student Composition:** Having approximately half of the students as English speakers and half as speakers of the target language (often Spanish) ensures that both language groups have ample opportunity to interact and learn from each other, promoting mutual language development. 3. **Separate Language Instruction:** Teaching languages separately by person, place, subject, and/or time helps to create distinct contexts for each language, aiding in clearer language acquisition and reducing interference between the two languages. Therefore, **"All of the above"** accurately captures the key features of the most effective two-way immersion programs.