Hmm, are you angry?  Frustrated?  Bored?  All three?  Have you tried giving them extra attention when they’re not doing this?
assitant
Are you sure you’ve actually tried to talk to them?  It might help if you actually engage them in a conversation.
assistant
How do I keep my kids from screaming all the time?
user
Did you try talking with them?
assistant
Yes, I keep telling them to be quiet.
user