If you are asking about teaching Linguistics, An Introduction to Language, by Fromkin and Rodman 11th ed. (2017).

If you are asking about foreign language instruction, The Common Sense of Teaching Foreign Languages, by Caleb Gattegno (1976).

In either case, Reading can be supplemented by your teaching them the beginning lessons of a language no one in the class knows, thus letting them experience language acquisition from the learner's perspective.

For English language introduction and learning, Cambridge university has some really good books like English around the world by Edgar Schneider

Emergence and Development of English by William A. Kretzschmar, Jr

Basic linguistics is the one that my professor used during my bachelor's study. That was an interesting read, where you learned morphology, syntax, and many other case studies...