You can do this a couple of ways:
1. The Painful, Drop Lowest Scores Method (explained here with dropping 2): http://jaredstein.org/2008/12/16/dropping-lowest-2-scores-in-blackboard-or-moodle/
2. Create a calculated column that looks like this:
Where Qi = a quiz. Note that the parenthetical can be replaced with another calculated column that simply sums up all the quizzes, so that'd look like this:
This 2nd method does not take the highest scores, but rather sets the max points possible at 100.
The 'Export to Spreadsheet' button is only available if you have the right permissions to the container - basic access to the gradebook doesn't give you the export button.
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