In the U.S., you must become a licensed teacher before you can teach ESL. Along with possessing a bachelor's degree from an accredited college or university, you must also meet the minimum educational and testing guidelines outlined by your individual state. Although requirements vary by state, all school systems require standardized testing to obtain a teaching license.
If you plan to gain ESL certification to teach outside of the U.S., you still need a bachelor's degree but do not necessarily need ESL teaching certification. Requirements vary by country, but generally you must gain a higher certificate or other qualification to teach ESL.
TEFL, or Teaching English as a Foreign Language, consists of basic training that offers certification to teach ESL in some places. TESOL, or Teaching English to Speakers of Other Languages, refers to the same type of training. While a TEFL/TESOL certificate is required for nearly all ESL positions, most employers require further certification. Typically, teachers find TEFL/TESOL training useful when teaching English to others within an English-speaking country, but not as helpful when teaching English in non-English speaking countries.
The CELTA, or Certificate in English Language Teaching to Adults, possesses widespread international recognition and reigns as the certification of choice to those who teach ESL outside of the U.S. Widely available and commonly required for those who choose to teach English in any capacity, the CELTA remains a popular route to ESL teaching certification. Administered by the University of Cambridge, the CELTA maintains a high standard for ESL certification.
The DELTA, or Diploma in English Language Teaching to Adults, maintains an even higher standard than the CELTA. Considered a follow-up to the CELTA, the DELTA is obtained by those who already have extended experience teaching ESL. The highest diploma in TEFL/TESOL currently available outside of a master's degree, it possesses international recognition.
Yet another option for certification, obtaining a master's degree in teaching ESL, can command better pay and more job opportunities. Several degrees exist, such as a Master of Education in Teaching ESL, a Master of Arts in Teaching ESL, and a Master of Arts in ESL and Applied Linguistics. Once completed, a standardized test in the teacher's state of residence will grant certification. If teaching outside of the U.S., check with the respective country's rules, as the CELTA may still be required in some places.