AZQQ provides these descriptions of ESL levels to help you think about how to apply the learning materials on this side to the lessons that you teach your students.
 
Level 1: Beginning
This student is often a new arrival with little previous English training and --this is the key -- a very limited vocabulary. This student is lost in the classroom and has nothing on which to base his ability to function, comprehend, and respond.  The student has no knowledge of English beyond answers to simple questions like "What's your name?" He/she may respond with "yes" or "no," but not always consistently or correctly. He/she may not be able to write in Western script. He/she lacks sufficient vocabulary and oral comprehension to be able to follow directions or do simple classroom assignments. This student may have no knowledge of the American classroom and its participatory style. He/she is not able to work at grade level, even if he/she is placed in first or second grade.

Level 2: High Beginning
This student can understand some classroom directions and attempts to do simple assignments but with great hesitancy and misunderstanding. Vocabulary is still greatly limited to commonly-used words. He/she reads and writes with great difficulty, usually below the assigned grade level. This student may be unable torespond to some activities which involve independent decision making, due to differences in the American classroom or teacher style. This student responds very positively to extra attention from the instructor or other students.

Level 3: Intermediate
This sudent participates in most classroom activities and follows directions adequately, though with frequent misunderstandings.  Vocabulary is limited but rapidly improving.  He/she may feel comfortable enough in the classroom to respond orally, despite frequent errors and incorrect word selection. This student may be able to do academic work close to grade level but needs frequent writing and vocabulary support. He/she exhibits growing confidence in his/her ability to comprehend and respond in English.

Level 4: High Intermediate
This student easily participates in classroom and social activities, constantly adding to his/her knowledge of vocabulary, American culture, and teacher expectations. His/her speech still exhibits a considerable accent, but grammar and vocabulary errors should be receding. This student's English is changing rapidly at this point, and his/her confidence level should be increasing at the same rate.

Level 5: Advanced
This student is able to participate and excel in all classroom and social activities, requiring less frequent teacher intervention with vocabulary and directional assistance. He/she should be able to read at near-grade level with the help of a dictionary, but writing skills may require more teacher support. A noticeable accent may still be present, depending on the age the student was when he/she arrived in the US. This student can function adequately at grade level and often does extremely well because of a high motivation level.

Additional Information on ESL/ELL Levels

The national TESOL (Teachers of English to Speakers of other languages) standards will give you more specific descriptions of levels. Click here.