lots of people wore jeans yes, but not scruffy looking. Some people were dressed smarter than others; so I wore yellow jeans and a nice jumper, some of the boys there were wearing suit trousers and smart jumpers, some people wore chinos. So long as you look clean cut and respectable just wear what you normally do. “Smasual” (as we call smart casual at my school) is a good guide. Good luck, I’m sure you’ll be fine!