Who knows about children services social services?

I have my 15 year old granddaughter who is mentally handicap , autisic and developmentally slow . She is still in diapers and behavior is that of a one or sometimes two years old , she is also combative to self and others , but she is a sweetheart only wants all of the attention from you all the time . I have had her sence she was five months old!! now I want to keep her but I can not take my grandson who is feeling as if he is 17 years old and grown .He does not want to do his school work, just simply wants to play and making money selling candy at his school and buying games , Ipods, skate boards, gang looking caps, he is out of control and I want to send him to children services ,but I have been told if I call for children services to come and get him ,they will also take my granddaughter, who can not speak up for herself, nor can she protect herself, so is this true!! He may know this ,he knows the system well and fools so many people but soon they find him out . You see it is not that he can not do his school work but he sats and writes rap words and talks with his school friends during cl, so now the teachers are tired of some of his lies and behavior and he listens to nothing I say but I want to be able to keep my granddaughter!! not a rebelling teen ager !WHAT CAN I DO gramdma! I have tired all I know to make him understand . I also told him, you are going to be so sorry next year when you are 18 and in the 12 th grade and do not p!!!