Learn Dutch: Ik ben de student en u bent de docent. - I am the student and you are the teacher.

U is the formal word for 'you' in Dutch. You use it when speaking to someone older, a person in authority (like a teacher!), or someone you do not know well. In this sentence, the student is being polite to the teacher by using u.

Why does the verb change from ben to bent?

The verb here is zijn (to be), which is highly irregular. For 'I', you use ik ben (I am). For the formal 'you', you add a -t, making it u bent (you are).

If this was a question ('Are you the teacher?'), would it be bent u or ben u?

It would be bent u de docent?. With the informal jij, the -t disappears in questions (like ben jij?). But with the formal u, the verb always keeps the -t even when the verb and subject swap places.

I learned the word leraar for teacher. Can I use that instead of docent?

Yes, both mean 'teacher'. However, docent is typically used for teachers in high schools, colleges, and universities. Since the speaker calls themselves a student (which in Dutch usually implies studying at a college or university), docent is the most natural word to use here.