How come they have an American high school graduation when the programme is set in Britain?

In the graduation দিন episode the characters have an American High School style graduation with diplomas and a valedictorian. However the it is supposedly set in Britain where this doesn't happen and আপনি don't get diplomas when আপনি leave high school and don't need credits to graduate, আপনি just leave school with whatever GCSEs অথবা A levels আপনি sat.