Learn Hardcore Japanese: watasi ha sensei tosite gakusei ni nihongo wo osiemasu. - As a teacher, I teach Japanese to students.

として means “in the capacity of” or “as.” When you say 先生として, you’re specifying your role—“as a teacher.” It’s an adverbial phrase modifying the main action (teaching).

Why is に used with 学生 and を with 日本語?

Because 教える is a transitive verb:

The thing being taught (the direct object) takes を → 日本語を教えます.
The recipient (the indirect object) takes に → 学生に教えます.

Why is 私 marked with は instead of が, and can it be omitted?

は marks the topic (“as for me…”), setting the stage for what follows. が would simply mark the subject without that topical nuance. In natural speech, you often omit the topic if it’s clear from context, so dropping 私は is fine:
先生として学生に日本語を教えます。

Is 教えます present tense or future tense?

Japanese present/future is the same form. 教えます can mean “I teach” or “I will teach,” depending on context.

How would you change the sentence to past tense?

Switch ます to ました. You get:
私は先生として学生に日本語を教えました。

What would happen if you used 先生に instead of 先生として?

先生に would mark “teacher” as the indirect object—“I teach Japanese to a teacher.” That flips the meaning. として is needed to express “in the role of teacher.”

Why is the verb placed at the very end of the sentence?

Japanese follows an SOV (Subject–Object–Verb) order. All objects and modifiers come before the verb, which then completes the thought.

Can you reorder the phrases (e.g. put 学生に before 先生として)?

You can shift some adverbial phrases for emphasis, but because 先生として directly modifies the subject role, it’s most natural right after 私は. Swapping too freely can sound awkward or change the nuance.