Five-year-old Tahani is entering a school where English is the only language spoken, but in her home, her family uses a combination of both English and her family's native language. When she starts school, she takes a test measuring her English language development. Her score is well below that of the other children in her class, most of whom live in homes where only one language is spoken. Which of the following is the most likely explanation for Tahani's test scores?

The explanation for Tahani's test scores is:

Because Tahani speaks two languages, her proficiency in them will come later than in the rest of her monolingual classmates.

Explanation:

The reason behind this answer and phenomenon is that in the first place, Tahani comes from a house with two languages spoken to live life. Therefore, she is going to learn two different languages throughout her growth in that house. Making two times the effort her monolingual classmates will make to achieve proficiency in their lives. So, she is going to achieve it but later because she is working one time harder than her classmates.