I work in ESL. I learned Spanish in the DR as a kid. It took me months before I had learned enough to actually have a conversation. My teachers expected me to do math and science before I knew Spanish. I aced all the English classes. I was expected to write the lessons as they were dictated in Spanish - even though I didn't understand them. It wasn't until the last month of school that I actually was asked to memorize a specific paragraph to recite to the class. Everyone else had to memorize the whole chapter, and be able to recite any paragraph requested.
Now, switch to English. Try to ask a kid to write down what they hear in English. The word 'spelling' comes to mind. The math even becomes a bit illogical when we talk about measurements, but the numbers are the same. And the periodic table can be memorized as well as the formulas. In elementary school, we don't teach any foreign language in our area.
Age and education influences the ability a person has to learn apparently , so if you are young and have been in school, you have the best chance to learn the 2nd or 3rd language.
I see the use for bilingual education so kids can continue to increase their knowledge while building their English.
The parents, on the other hand, have disadvantages. They have age, and maybe education that influence their ability to learn the new language. Then their is exposure.
We expect people to be 100% integrated into society that has little tolerance. I have students, eager to learn English, telling me how they can walk in to a store, and have the security guard following them, and little ladies covering their purses. The minute they open their mouths, or when people see the color of their skin, bam, prejudice. And I've heard this from a 65 year old man, and a 25 year old man in ESL classes. I watch the 16 year old Chinese kid with learning disabilities becoming more proficient every day. In five years, he will be awesome. Then there is the little 50 year old lady with a 4th grade education. The English is just not sticking. Some schools charge tuition for the classes.
I have a college education. Learned the basics of 2 new languages by the age of 16, and started learning 2 new languages in my 40's. There is a big difference in how my brain works now. And I give all the credit to what I learned before I started college.
It is of the utmost importance to learn the language where you live.
Depending on your age, education, and economic situation, it can take a generation.
My dos cheles, adjusted for inflation ...
mkohn