The College Adjuster only works if you have University. If you only have the original game, you can use Merola's multi-painting (
www.simchaotics.com) to change grades up or down.
However, like I said before, the best way to affect kids' grades is to make them do homework. Have you tried making the kids do homework? If they do homework, the next day when they come home from school their grades will go up. If they don't do homework, their grades will keep going down every day.
If you do not know how to make the child do homework, there are two ways:
1) When the kid gets off the school bus, watch very carefully and you will see the child carrying what looks like a folder or clipboard. This is the homework. Watch where the child puts it down (usually on the floor or on the ground outside). Click on the homework object and you should see an option that says "Do Homework".
2) Install Macrotastics (available here:
http://www.moreawesomethanyou.com/smf/index.php?topic=208.0) and then click on the child and choose Macro...Do Homework.
Hope this helps.
Karen