I'm of the same generation Janet is...
I think teachers should dress up more than the students do for sure. They're supposed to be setting an example, and being well dressed is part of that in my mind. I don't think skirts should be mandatory, but dress pants rather than jeans... nice shirts or sweaters rather than sweats or tees... leather shoes rather than sneakers wouldn't hurt.
I've had MANY jobs over the years and all that put me in any position of authority demanded at least office casual dress. It's ok to show the students that this is how adults dress in the workplace. I personally am totally turned off by adults who show up to work with cleavage or bellies showing. I'm seeing a trend toward that in our new teller at the bank, and it just isn't appealing or professional. If you want to be seen as a professional, you need to dress like one.
JMHO