Erasable Pen Method

They sell erasable ink now, you can go to any store and buy one. This may not work for some tests though, but if you do, do the test with this pen, and if you get to check it yourself, when your teacher says to "get out a pen and she better not see a pencil" take off the eraser part and put it in between your legs or something, then when you go to check it, erase the wrong answer and write it back, it's in ink so she won't suspect a thing!