When a student takes a test or quiz, studying is the best way to go but is not the only factor in that student's performance. In math, I believe that being prepared to take a test also includes having a pencil and a calculator. And I also believe that the pencil and the calculator should be the one's that that student uses everyday.
When a student uses pen in math I think it messes with the student psyche. With pencil, you are able to erase mistakes and move but if you write in pen, you are constantly reminded of your mistakes. Not the impression you want to mentally give yourself. Students are also less likely to take risks in pen since it cannot be erased so a more challenging problem is a whole other element for them.
Not having a calculator on a test can also mess a student up. My students do not use their calc for every problem but it is a great tool just to check the arithmetic and not have to worry about that part. It is important that the student uses the calculator they use everyday on the test, when they borrow a calculator it may be a different version and that can throw them off. Formulas are stored differently and buttons are shifted around.
Having a pencil and calculator for any math test can be a security blanket for students and make them feel more prepared than they would be without them. I remember in college that if I was up studying late for a test or presentation I also took a shower and dressed up--it gave me the confidence for the task at hand. It is the same concept when you take a math test, when you have your own materials you feel confident, when you are missing materials you feel (and are) unprepared and that can reflect poorly on the test.
When a student enters the math classroom with their own materials, they only have to worry about taking the test!
Educator who loves math and working with students.