It is widely believed by many native speakers of English that, because they know English, they are qualified to teach it. However, this isn’t the case, as before going into a classroom, it’s necessary to know skills and techniques such as:

• classroom management & instruction giving,

• how to grade your language,

• how to analyse and teach vocabulary/grammar,

• how to check understanding and use error correction techniques,

• the different between STT (student talking-time) and TTT (teacher talking-time).

The CELTA covers all this and more, and includes 6 hours of assessed teaching practice, which is another reason it is so well respected.