Busy work is a term for work or assignments that are time consuming, but not useful. It is typically used to refer to schoolwork

Schoolwork

Schoolwork is work assigned by a teacher, school, or other educational institution. The term generally refers to both work completed at home , as well as work completed during class . Typically, schoolwork is done in class, during the time period allotted by the instructor...

which is time consuming for students but not educationally valuable, but can also refer to procedures or paperwork in a bureaucracy which is unnecessary. The term is generally pejorative.

Busy work in academics

Within academics "busy work" can refer either to classwork assigned for the purpose of keeping students busy, so that they do not cause trouble, or to time consuming homework which is assigned as practice, but is of little educational value. Teachers are often forced to complete busy work in the form of maps and scales.