I signed up to volunteer at the library in my son's high school, figuring they needed someone to sort books, make copies, etc. Yesterday, when I went in for training, I learned that they actually need someone to run the library, supervise its computers, and act as an authority figure for students while the librarian is teaching in the afternoons.

I'm okay with this. I have library experience and have taught in a volunteer capacity in the past. However, parenting aside, I've really only worked with much younger kids. I'll be there at least one afternoon a week for the duration of the school year. Any advice on what to wear when working with teenagers?