There are two basic ways to start a new semester with the same bunch of kids. Which you choose depends on your preferences. If you have a seating chart in MTG that you don't want to change or mess with, I would choose Option B, the so-called Phantom Carryover.

Option A: Importing

1. Open MTG as usual.
2. Use Control-N to create a new class.
3. When the Create New Class Screen appears, you should see a button that says, "Import All WITH Roster." Click it.
4. When it asks you if you want to review the setup information, click yes, unless you're positive you don't want to make any changes. If you want to make sure, click yes, and then "next" your way through the screens that follow. You may want to type "Spring" in the first window's Academic Term box.
5. Make sure when you are done "nexting through", that when you save (Control-S), you save it with a different name than the first semester class you imported from. I would suggest adding "spr" or "-2" or whatever to distinguish it from first semester. If you get the box that says "There is already a file with that name", say NO or you will overwrite your first semester's grades.
6. Repeat for each of your classes.

1. In this option, you don't actually create a new class. This is the option to use if you want to preserve your seating chart from first semester.
2. Open a class.
3. Go to the Edit menu and select "Drop/Undrop assignments." You can also use Control-D.
4. Now, just Drop all the first semester assignments. (This is not the same as deleting! You can delete if you want, after you drop, but there really isn't any reason to). What this does is "keep" all those assignments, but greys them out and doesn't calculate them into the total grade. This lets you check how the student did first semester, but only calculates second semester grades! This also preserves your seating chart from first semester.
5. Use control-S to save, and repeat with the rest of your classes.