Plymouth - Does Anyone Know What This Was?

[10ClarionSt]

I was visiting Plymouth at the week end and was in the Barbican on Sunday afternoon when an open top bus came up the street with a lot of youngsters on board parading a large trophy. They were chanting "Champions, Champions", so had obviously won it for something. They were all in uniform so I wondered if it was perhaps a brass band thing. Must have been important for them to hire an open top bus. Anyone from the area know what this was? I couldn't see the banner on the bus from where I was, so didn't know what they were celebrating.
Thanks.