I work with a volunteer organization that teaches English to Burmese refugees, from ages 7 to the mid-40's. Most of the refugees arrive in America with little or no language skills, however there are those that have been living here for a year or two, and they have an intermediary understanding. The volunteer teachers have no, or very little, ESL teaching experience, and a portion of volunteers work only for a short stint. Most volunteers do not prepare lessons beforehand. Classes are twice a week.
So, this is our challenge: we need to buy excellent ESL textbooks that guides the student (of all ages) through the progressive phases of learning English, while also allowing the volunteer to arrive without preparation. The volunteers should be able to open the textbook and teach a lesson just by looking at the chapter's content; the student should not get bored by uninteresting or outdated material. The textbook lessons should include vocabulary, grammar, and conversational practice.
It has been recommended that we buy the New Headway textbook series, designed by Oxford University Press, but reviews I've read say the content is outdated and boring.
Which textbook series is best for our unique situation?