Can a teacher force someone to do something after school?In the US, forcing is really not an issue. Force isn't in play in a classroom and students of any age can and do act as they see fit.
there are consequences for choices. If those consequences are not what you want, then the alternatives may be better. No one can force you to do homework, but the teacher will let you know what the result of that choice might be.
If you enroll in a class where an assignment is to attend a play at the university theater and write a review, then there should be no problem since you willingly joined the class (or school or program etc).
In the grown up world, sometimes you will give up things in order to receive others and the choices are often not something you like.
A teacher has no police authority, nor any other authority to force any one to do anything. However Any teacher will be supported by the school administration, in requiring students to participate fully in the activities of the class including related work in school and out of school. Refusal on the part of the student would result in not receiving a passing grade, and possibly other penalties as required by the administration.
Forcing someone never leads to a positive outcome. A teacher can inspire, motivate and allow her students to grow on their own terms. If a student however, is too stubborn to even lift a finger and participate in extra curricular activities to hone himself to be better, it would help to expose the student to different areas that he might be interested in. Then let him unfold on his own.