Does DHS have the right or can they question my child without my consent?

i live in oklahoma, can the department of human services go to my childs school and question them without notifying us? i am very pissed this happend. please dont joke about this , if you have some input please help me.!!!!!! scenerio........my wife was trying to her 14 year old daughter and in the process she got scratched on her neck with her moms rings. thats what happend she was arrested for domestic abuse and now i found out today , DHS was at our childrens school questioning them. is this legal???