In the area where I live (SW Cumbria) they use the expression:
Where's your school bag at?
I always assumed this was a particular dialect, because in the English I speak this phrase is wrong, and I would simply say:
"Where's your school bag?"
But recently I heard a similar phrase from a North American, and I wonder if it is standard in American English.
Interestingly round here they also never use the word 'trousers' but say 'pants' instead, which still causes me confusion at times.
Or is all this actually standard in the UK these days, but I'm just behind the times?