Ah, my dear, young, stupid grasshopper:
1) If you really wanted to be a successful grade-alterer, you should have paid more attention to your penmanship over the years.
2) Blue ink over black type is a pathetic and dead give away.
3) Once you go down that road, there is no turning back. You have to keep track of which grades you changed, and what you changed them to. It's almost as complicated as math.
4) This one you know already, which completely dumbfounds me... Your teachers email progress reports weekly. I already knew the truth.
5) Please...You have the high school hi-jinks mastermind (that's HSHM, for short) for a mother. What is it those crazy kids like to say these days? Ah yes... Been there. Done that.
6) Your punishment will not be for the grade, because in all actuality it isn't that bad and it is only mid-quarter. You will have plenty of opportunity to visit your teacher after school and possibly be introduced to a tutor. The punishment is for the deceit. I am not a big fan of withholding/lying about information. Not good, Mister Not-So-Smarty-Pants. Why don't you take a look at that geometry book while you are sitting in your bedroom with no phone/tv/computer all weekend? You just might learn something.
7) Oh, and before you try to trick your substitute teacher into believing that YOU are the substitute already assigned, and she can leave and enjoy her afternoon, please see #5.