Is the word teaching a verb?

Yes, "teaching" can be a verb. It is the present participle form of the verb "to teach".

Here are some examples:

* She is teaching English to young children. (present continuous tense)

* I enjoy teaching music. (present tense)

* He has been teaching for over twenty years. (present perfect continuous tense)

While "teaching" can also be used as a noun (e.g., "The quality of his teaching is excellent."), in your example, it is functioning as a verb.