Adult education classes generally attract students of widely ranging ages.
Often students in their late teens will be taking the classes in order to get into GED or vocational classes.
Young adults may be taking classes because they need to speak and write English to get a good job.
Middle-aged adults frequently take classes to improve English skills for promotion in their jobs or to change careers.
Older retired individuals may be taking the classes now that they finally have time.
The wide range of ages suggests that you may need to use a wide variety of activities in the classroom in order to reach all of your students. It also suggests that you can often be most effective by grouping students and doing many activities in the small groups. Age is one natural way to group people.