"Er richtet sich an den Lehrer."

Translation: He directs himself at the teacher.

[cornalie]

Not at ,but to (direction ) , at means hostility

[JonathanRoberts]

He faces the teacher?

[cornalie]

He speaks to the teacher .
He goes and sees the teacher
He goes and speaks to the teacher
He addresses the teacher.
Sich richten an + akkusativ