prepositions - Out or out of which is it?

Which is correct
1 Get out the house. Or
2 Get out of the house?

I've heard that the American English standard is the first one and the British English standard is the second one. Is that true? The Oxford dictionary says in a side note that out as a preposition is standard in American English while the prepositional phrase out of is standard in British English while saying out is not standard.