Gradebook

My reply may be too late, but I thought I would take the chance anyway.  I have the same situation (in the "Grades" section).  My solution is to exclude the practice quizzes from the course total calculation.  To allow students to see their practice scores, I use the "Edit Categories and Items" (also in the "Grades" section) to sort the graded items from the ungraded items (graded items on top).  To further distinguish the graded items from the ungraded, I include the percentage contribution of each item to the total in the title (e.g., Assignment 1 (10%)).  This is done in the "Edit this Assignment" area.  When students view their grades, they know their grade is based on only those items that have a percentage contribution amount in the title.