I feel your pain! I have a screecher too. Shes part time and only has just started this "screeching like a banshee" type scream and it drives me nuts. What I have been doing is giving her a look and firm "ssshhhhtttt" like Cesar Milan does LOL and it seems to work temporarily. If she does it again, she goes into the time out playpen in my dining room and if it continues she goes upstairs for her nap early. I feel terrible but don't know what else to do. Its so awful to listen to and it immediately sets off all my other babies in my care. Crying with tears is one thing, this screeching like a banshee scream is purely attention seeking which I will not tolerate.
This 1 year old just started with mom. Mom says they are working on it at home and Mom knows what I have been doing here. Hopefully it stops soon.