Even when CPS finally pulls kids out of a home, it's not necessarily an improvement. Plenty of kids get beaten, sexually abused, and neglected in some (not all!) foster homes. That's one of the reasons CPS workers are often reluctant to take kids -- they know they don't necessarily have a better place to put them ...
I've been in child psych nursing, as a staff nurse and then as a CS, for 15 years now. It is definitely not for the faint of heart -- what I have always told students and others who ask is, "the highs are higher, but the lows are lower" than adult psych nursing. What you are describing is certainly one of the "lows" or "dark sides" of child psych. Abused children are always going to be a sizeable percentage of the population in treatment (outpatient as well as inpatient), and they (and the situations in which they're trapped) stir up a lot of emotions in the staff caring for them.
IMO, a big piece of being successful in either adult or child psych is finding your own, unique balance of objectivity and subjectivity -- if you're too detached, you don't do the clients any good, and if you're too emotionally involved, you don't do them any good, either. The balance is a little different for everyone (and some people never manage it).
I don't have any "quick fix" answer for you that will make everything fine. I hope that you are getting support from your administration and more experienced co-workers, and have an opportunity to process and debrief these emotionally draining work issues. Do you have an opportunity for structured clinical supervision at work (an opportunity to process on a regular basis with a designated, experienced colleague (someone other than your boss), to get feedback and guidance)? If not, you might want to ask about whether that could be set up. Clinical supervision (esp. for people new to psych) used to be a regular part of the structure of psych units, but it seems to have fallen by the wayside in more recent years -- I think that's a big mistake.