backfired

My girls are always screaming at the top of their lungs, usually in the house right as I get Kaydree to sleep or in the car, where we are all able to hear a little to well, they scream and scream, not mad screams just play screams, but I am always telling them to use inside voices, but when we are outside they can scream as loud as they want, but not to do it when they are indoors or in the car! So...the other day the girls were out of control, like more than usual, everything they were doing was naughty, I couldn't believe it, and I had had it, so I started screaming at them, telling them to knock it off and so on so forth, I gave them a bit of a lecture on how they needed to act and what things were naughty and what were not. Well, Kallie in a soft voice says "Mom, are you outside? You need to use your inside voice, you can scream really loud at us when we are outside playing, but you need to yell quietly now because we are in the house." BACK FIRE! Why can't they listen when I want them to? I guess they do hear everything I tell them!