> using a calculator
Students who are at a level where they'd be learning to do the computations a calculator does, shouldn't have graded homework. And even at that level, real mathematics is more than just computation.
> getting answers from previous tests
Decades ago, my teachers and professors knew advanced tricks for this, like "not just reusing the test questions from last year". Sometimes they even changed the constants in math questions between sections of the class.
Reading previous tests (including correct answers) was never considered cheating, or even slightly unethical, in my education. In fact, one of our professors had this party trick of working through all the answers for a past-year exam (perhaps multiple of them; I can't recall the details, but certainly much faster than students were expected to work things out under exam conditions) in the space of a single lecture, near the end of the course. Students were meant to see this and learn from it (as well as be impressed).
> resubmitting assignments
Why would you ever not notice this?
