Here are my top 3 ESL textbooks for adults. While they are all 4-skill books, the focus in all of them is primarily on speaking, with a nice variety of communicative activities perfect for beginners to advanced students. They’d all work well with high school or university students and adult ESL learners.
“Smart Choice” by Ken Wilson is a great choice if you want to make your classes interesting and educational. The pages contain a good mix of information presented in a clear way and practice exercises. The topics are reasonably interesting for university students and there isn’t much in the way of irrelevant or annoying stuff. Overall, I would strongly recommend this series for young adults at the high school or university level.
World Link makes an excellent choice for beginner adult students
World Link has so many great activities in it that you won’t need to spend a lot of time doing additional prep. They present the grammar and vocab sections in a simple way that’s manageable for a single class. The teacher’s resource book and teacher’s guide also come with lots of useful supplementary materials. Although it’s a 4-skills book, the focus is mostly on speaking.
Four Corners is an excellent 4-skills book with a heavy emphasis on communicative spoken activities. The students are active, engaged and interested in the topics and the grammar and vocab are nicely presented in a way that’s really easy to understand. A great choice for your high school, university of adult ESL classes.