Step-by-step explanation:
I agree with the Mothers comments considering the following:
1. The Intelligence test may have tested in a language he understands very little: Note we are told he is from Mexico where the official language spoken is Spanish, so he may have performed better if the test were in Spanish.
2. Most immigrant Hispanic parents work more hours trying to cater for their families, thus since Juan is the firstborn he may have to cater for the needs of his younger siblings with little study time.
I agree with the Father's comment because the American educational system is more likely different from the one in Mexico, as such Juan may yet have become accustomed to it, thus the American educational system doesn't do enough to allow immigrants adapt to the new educational system.