RESOLVED 4:34pm PDT:Google has notified us that the issue with App Engine Over Quota errors affecting Teacher Dashboard classic was resolved as of 2:52pm on Tuesday 2015-03-24. We sincerely apologize for any issues you may have experienced. Thank you for your patience and understanding during this service disruption.
UPDATE 2:15pm PDT:
We have received multiple reports of Over Quota errors for users using Teacher Dashboard Classic. Our developers are investigating this issue, and we will post updates to this blog as we progress. PLEASE NOTE: users using Teacher Dashboard 2.0 at www.teacherdashboard.com are unaffected. Thank you for your patience and understanding.