Bug, the 10 year old, forged my ex-husband's signature on a letter that got sent home because she had not been turning in her schoolwork on time. Ex & I agreed (shockingly enough) that she should be grounded (she usually does really well in school, and her behavior is pretty good most of the time, too). I began her grounding the next day, which was a Thursday, but my ex didn't start her grounding because he ALWAYS sends the kids to his parents' house on his weekend. Mind you, he has a one and a half year old that doesn't go to his parents, just Bug and Bubber. Bubber told me they HAD to go to the grandparents, because my ex HAD to work on cars on Saturday (this is not his regular job, but a side job he does with his wife's cousin, and certainly not a job he has to do every weekend). Apparently his desire to make extra money and get the older kids "out of his hair" for the weekend overrides the necessity for our daughter to learn that she can't do things like forging signatures and lying. Of course, I wonder who was watching his other child if he HAD to send the older ones to his parents' house....
Anyway, it looks like most of the people who voted agreed with my opinion that the discipline comes first. Period.
So thanks to everyone who voted - I'm glad you took the time to let me know what you think!!