We are preparing to upgrade Moodle from 2.2.1 to the latest 2.4 stable release. In doing a dry run, I have not been able to perform the upgrade with the Attendance module in place. (It complains that it can't find an updated version of Attendance.) I thought manually downloading the 2.4 plugin and pointing to it would do the trick, but it didn't.
In order to successfully run the upgrade, I've had to delete the module and then, after upgrading Moodle, put the appropriate version of Attendance in. This, of course, deletes the past attendance history. This isn't impossible for us to deal with (the actual upgrade will be in between class terms, and a copy of the old installation will be available for anyone who needs it), but it would be nice to avoid it.
Is there any way to handle the upgrade without losing the old attendance data?