You reap what you sow.
Here is our tale of reaping what you sow for BM. SD17 is a senior this year, since her 8th grade year her grades have been crap so she lost her cell phone privileges when she was with us. Her BM got her a phone and gave it to her when she was at her house. She brought her grades up one semester so she could get her phone back then they tanked immediately. So she lost her phone again at our house but kept it at her BM's. We have tried enforcing rules with her, tried keeping her on track and BM fought us every step of the way.
She would fill SD's ear with all sorts of nonsense. Bashing SO and I for trying to keep her on a good path. Saying that we were mentally abusing her,how it wasn't right for her to be grounded when she brought home a 1.6 GPA report card. If that is all she is capable of doing then its not her fault. Everything we tried to do just went no where. If we would have had full custody I believe we could have made a difference. But BM wouldn't give up her paycheck/CS so there was never a chance of that happening.
So here we are SD will be 18 in January, shit grades, bad attitude, disrespectful to teachers. She stays in line at our house, no disrespectful attitude, no talking back because we would line her out real quick.
Well BM calls SO today leaves a tearful VM that "we need to talk" SD is out of control, we are going to have a problem when she turns 18, her bad attitude is too much for me to handle and on and on. So now she expects SO to back her up and get SD in line at her house even though she blocked us every chance she got. SO is debating whether he is even going to call her back. He feels like she created this mess and now she can deal with it.
I am staying out of it because I have pretty much disengaged from SD, we still have a relationship but I don't have any say in her grades and discipline anymore because I saw this happening 4 years ago.