British English. Being an immigrant family, my parents were a product of British-influenced schools, and many of the books in our home, including the dictionary, were published abroad. My American teachers used to dock me for using UK spelling, and a few even made me serve detention for continuing to use it. (My Dad used to go ballistic when this happened to us, and would invade the principal's office, dictionary in hand, to prove that I was *not* incorrect. Then, another year and a different teacher, and it would happen again...)