I went to high school in the 1970's and am tortured trying to identify the name/author of a short story we read. All I remember is portions of the story line.

The story was about a teacher (writing teacher I think) who assigned the class to go research and write a paper about a fish (a pike or Mackerel I think). The next day the teacher assigned them the same assignment to dig deeper and write more about the same fish. This goes on for several days.

I would me most grateful if someone could help me identify this story which tortures me.

Thank you.