(cliché, also attributively)A stereotypical unconvincing excuse for not completing school homework, or (by extension) not meeting one's obligations.
2011 May 6, Damian Carrington, “Environment action delays blamed on 'dog ate my homework' excuses”, in The Guardian[1], archived from the original on 2022-08-24:
Their reasons for missed deadlines are mostly of the "dog ate my homework variety" including such easily foreseeable events as yesterday's elections and that the badger culling policy is "difficult and sensitive".
2014 September 12, Oscar Webb, quoting Donald Campbell, “UK Government Changes Its Line On Diego Garcia Flight Logs Sought in Rendition Row - Again”, in VICE[2], archived from the original on 2022-12-05:
The government's excuses for Diego Garcia's missing records are getting increasingly confused and desperate. Ministers could hardly be less credible if they simply said 'the dog ate my homework.'
2017 February 18, Mia Berman, “Go West-minster, Young Mastiff”, in HuffPost[3], archived from the original on 2019-04-09:
Our immune system's weak; we've been sick as a dog, missing work and school, resorting to "the dog ate my homework" excuses amidst these frigid dog days of winter.
, Oxford: Oxford University Press, launched 2000.