Here are some examples:
* If you know the teacher's gender:
* He/She (singular, depending on gender)
* They (singular, gender-neutral)
* Him/Her (object pronoun, depending on gender)
* Their (possessive pronoun, gender-neutral)
* If you don't know the teacher's gender:
* They (singular, gender-neutral)
* Them (object pronoun, gender-neutral)
* Their (possessive pronoun, gender-neutral)
You can also use the teacher's name or title:
* Mr./Ms./Mx. [Last Name]
* [Teacher's Name]
* The teacher
The best pronoun to use depends on the context and your knowledge of the teacher's gender identity.