The wearing of jeans to work

Whenever I begin teaching a new group of students, I make an effort not to wear jeans on seminar days. This, I think, stems from my days as a postgrad teaching assistant, when I felt I had to look semi-authoritative because I didn't have any Dr. title to provide this authority. I tried then to project to the students (and myself?) an image proving I was qualified to teach them. I suppose I now do this as a confirmation of that. I set off with the intention of wearing 'tutor clothes' every week, but as term goes on I start to slip, and by the end of the year I'm wearing jeans to seminars. I figure by that point if they don't see me as their 'tutor' jeans won't make a difference (and I do like to promote equality of ideas and opinions between tutor and students in my seminars!). I have never given a lecture in jeans. This, I know, is a matter of maintaining my own confidence.

For my new admin job, I wouldn't wear jeans to work. Not as a spur to my confidence, but because my image of office/secretarial workers is smarter than that (smart casual, not necessarily suits). None of the other ladies in my office wear jeans either. Presumably they feel the same as I do.

There are only three men in the administrative unit in which I work. One at my level (lowly admin assistant), one is my line-manager's manager, and the other is my line-manager's manager's manager. Both top level administrators wear suits and ties for work. Lowly administrator wears jeans and a sweater or a casual shirt. No one seems to question this. No one seems to object. But I wonder what would happen if I turned up in jeans and a hoodie tomorrow? I'm sure someone would notice, and probably they would object.

So, ignoring my seminar jeans issue (which is, I acknowledge) entirely of my own imposition) what do you think about wearing jeans for work? Do you think its appropriateness is gendered? Am I imposing my own rules again?