ESL stands for English as a Second Language. Although we know that for many of our students, English is a third or fourth language, the acronym ESL seems to stick. EAL (English as an Additional Language) is more appropriate, but is not commonly used. ESL is a broad term that can mean various types of school-based programs and classes designed to help students learn English while learning the school curriculum.
No. While it helps to have some knowledge of the students' first language, it is not necessary. (And with some classes containing many first languages, it is sometimes impossible to speak all the languages represented!). Students seeking an ESL license must, however, take the equivalent of three college semesters of a foreign/ world language.
Bilingual Education, in essence, is teaching the necessary curriculum primarily through the students' first language. While students are learning part of the school's curriculum in Spanish, for example, they are also receiving support/instruction in English language acquisition through other areas of the school's content. This way, students can learn content in a language they understand while they acquire English. In sum, a bilingual teacher needs to be a skilled content area teacher, ESL teacher, and bilingual teacher.
Yes. Because you would be teaching the "regular" content in a language other than English, you need to be either fluent or highly proficient in that language. Most Bilingual programs in the U.S. are in Spanish; however, if you speak a language other than Spanish in addition to English, you are also eligible for a bilingual license in the state of Wisconsin. Candidates for the Bilingual Education License must pass the LTI Language Proficiency Test with a minimum of a "low advanced" in both the written and oral portions of the test. You can read more about the test here:
No. Just like you can't get a license from UW-Whitewater in ESL alone (an ESL license needs to be added on to a "primary licensure area"), a Bilingual License can only be added on to an ESL license. But, you may work on each license simultaneously.
ESL and Bilingual teaching licenses are "add-on" licenses. In other words, students "add on" an ESL license, and possibly a BE license to their "major licensure area." You might think of it like this:
Primary Licensure Area/Major  → add ESL Licensure → add Bilingual-Bicultural Licensure
However, while ESL and BE are "add-on" licenses, students actually work on all their licenses at roughly the same time.
Students are enrolled in a "primary licensure area," such as elementary education, special education, secondary social studies, English, science, or math, etc. Concurrently, students take coursework in ESL/BE in order to "add" an ESL license to their primary license. Additionally, students who are fluent in a language other than English may "add" a bilingual license to their ESL license.
You may add an ESL license to the following primary licensure areas: Elementary Education (MCEA); Early Childhood; a Secondary "Core Content" area (math, science, social studies, English); Special Education; or a World Language.
You may add a BE license to the following primary licensure areas: MCEA, Early Childhood, or a Secondary Core Content area.