Lamar, Turnie is right! I had one colleague who had a PhD in linguistics and who would turn up for work everyday in scruffy jeans and a creased T-shirt. By contrast, another colleague, who had trouble spelling his own name, would turn up for work everyday looking like he'd fallen straight out of a tailor's shop window. For the most part, no-one seemed to care.

As for me, well I'm a bit of a 'basket-case' insofar as I do not own any long-sleeved shirts. I hate them! Likewise with any type of long-sleeved clothing (coats excluded).

That means that even in winter I wear short-sleeved (dress) shirts in the classroom. Remarks often vary from 'You must be crazy' to 'Wow, you're so strong'.
That said, you are also correct insofar as we are all judged by what we wear. A teacher dressed for the beach is hardly likely to be taken as seriously (at least at first), as one who is essentially dressed for a formal dinner.