CONTROVERSIES
The U.S. is the country which has highest immigration rate every year, and many students from other countries come to schools. Those students often have limited English abilities so they cannot catch up with mainstreams. So, for these students, schools often provide special programs to help their English study and other subject studies.
<Bilingual Education Program>
Teachers teach both in students' first language and English in the classrooms.
<English as a Second Language (ESL) Education Program>
Teachers teach only in English in the classrooms.
<Difference between English as a foreign language and English as a second language>
English as a second language: Students are living in the society where people mainly use English.
English as a foreign language: Students are living in the society where other languages are mainly spoken.
Example: Japan (We study English but we don't speak English in our dayly life. We speak Japanese mainly.)

~Links for more information~
Bilingual education (In English)
Bilingual education and ESL education (In English)
Bilingual and ESL education (In Japanese)