Thats why it doesnt work , overkill, too many yelling sessions and spanking you are getting nowhere with that, try the opposite focus on their positive side and praise them when they do something good , children respond to lots of attention, if there is a Dad around get him involved with Games a nd sports and outside Activities.They are still young enough to use the time out system.seperate them if they are misbehaving together , no TV No PC or video games, set the bounderies and forget the yelling.
Yeah the yelling isnt going to help the situation. If you are going to use spankings, do it less than often. My brother and I got spanked when we were younger and it only took one spanking to stop us from doing it again. Why? When we were given a spanking, we were told we were in trouble (parents didnt yell) then we were sat down and we had to let them know we understood what went wrong. We took our spanks, and our parents calmly told us to go to our rooms.
The reason spankings arent always effective is because from the childs point of view, you may look as if you are acting out of anger and spanking them (this is what yelling communicates to children). Whereas if you spank, you need to find a way to communicate that it is a response to their actions, not a response to how angry you are (while you may not feel that way, that may be what they feel)
Give them consequences for not doing what they are told. Tell them once, and warn them. If they dont do it after that, then give a consequence that is measurable to the offense. But also stay calm when you are punishing them, because if they see you get angry or start yelling, the "teaching" part of the discipline is lost.
And also dont forget to focus on their postive side and praise them occasionally it isnt all about punishment.