Comment 2 for bug 1272181

You have already reported this issue: https://bugs.launchpad.net/schooltool/+bug/1266645
And I have already suggested to remove schooltool trunk ppa from your sources.

The version of python-schooltool should be less than 1:2.6.2~dev.20140105
So it is good it fails to upgrade. But you do see problems that appeared in newer version... It fails to upgrade, but starts?

To remove the trunk ppa,

  $ sudo add-apt-repository --remove ppa:schooltool-owners/trunk

Fix packages that failed to install

  $ sudo apt-get update
  $ sudo apt-get install schooltool/precise python-schooltool/precise

If I understand correctly what happens, schooltool now will fail to start with an error similar to "generation too high (have 43, expected 42)". You have to restore from backup older than 2014-01-05. But 20 days have passed since then, is the data important?