After college semester ends, who is responsible to turn in grades?

Answer 1

Professors are responsible for turning in grades to the registrar.
Today, this is usually done electronically.

If a course has teaching assistants who do the grading, they usually have to turn in their grades to the professor, who then submits them electronically.

There are always deadlines for grade submission. If a professor does not submit the grades in time, s/he and his/her department chair get a pointed email from the registrar's office. A department chair will then pester the professor to submit the grades.

Answer 2

The teachers have a deadline to submit grades so they can be posted for students to see after a certain date.