Marks

Your marks effect you a lot because if you don't hand in your work, your marks will go lower and lower, & that's a very bad thing. Cause you could fail the class if you don't hand in your work, which is called an "NHI" you could not graduate if you dint hand in your work in school, but when everyone graduates we need to find reasonable jobs so we could live a happy life and have a great future, your marks affect you a lot in life. 

Calculator

The good thing about calculators is it could help you to correct your math, say if you don't know if you got the answer wrong or right you could check, then fix the work but you have to show your work, the bad thing is if you never showed your work and just put in the answer on a calculator and write it down, you would never know how to do it, and that is a very bad thing.