Adding to what Dark Panther said: shutcha = shut ya = shut your. When you say "shut ya" fast, it sounds like "shutcha". It *is* rude slang and not very common, so I wouldn't go saying that to anyone. This is why I don't think learning English from movies & TV is such a good idea...

Shutcha heads is a (rude) slang. Shut= shut (i.e. to close) cha = your shut your heads = shut your mouths = shut up = be quiet When "shut your" is spoken quickly it sounds like "shut cha"

What sounds rude to some is actually normal southern drawl.

The guy is telling the kids to be quiet in a rude manner.

he could also say, "shutcha traps" or "shutcha holes". Another rude saying like these, is this: "shutcha pie-hole". The use of "shutcha" in itself is not what makes this a rude comment, but the fact that he says shutcha heads - this is what is rude. If I had someone working on my door, and when he was done fixing it, he said, "I'm gonna shutcha door now", then it wouldn't be rude at all. :)