What was the uniform like? Some wild blazer? I assume a school with some notable standing/history - my school didn’t have a flag, or even proper school uniforms - we had polo T’s and a round neck sweatshirt FFS,
It’s the flag of Devon, county in England officially adopted in 2006 (although variants have been used for ages)
It’s funny what flags can signify, the 'unofficial flag of Ile de France:
Has been reported to be an insignia of the far right in France and used to point to the gilets jaunes being far right. Yet it is a popular regionale flag (in the region where the protests took place). Admittedly it has royalist connotations however I highly question the adoption of it by the far right (royalists yes but the far right don’t want the royals they want the power for themselves).