thats good news about DD, I'm glad she is thriving in boarding school. You must be worried about Ds2 
i think the comments about " sending back" a child ( on the other thread and elsewhere ) are somewhat misplaced. All the adopted children I know who have had to return to the care system have not been at the " choice" of the parenst. Some were extremely violent - assaults with offensive weapons, bleach etc, sexually assaults on other children, killing pets. It was impossible for anyone ( police, social workers, psychiatrists) to ensure the safety of others.
Domestic violence doesn't become ok or tolerable just because the perpetrator is legally a child.
Others were impossible to live with because of addiction problems or false allegations, which put other family members at risk.
Many of these young people could not be accommodated in residential units because their behaviour was too extreme
So i dont think the parents concerned felt they had a "choice" or that they were sending " back" a child because they weren't good enough or measuring up to their expectations. Basically they were forced to make a choice between their children
