Is denim allowed?

Some schools that I have worked at, jeans are allowed, as long as they are 'dressy jeans.' However, where I currently work, jeans are not part of work place attire. The reasoning behind it is that our students wear uniforms, so the teachers should dress professionally.

Here's my question...is wearing denim (but not jeans) breaking the rules? In the outfit below, I'm wearing a denim skirt. Technically, it's not jeans but it is made out of the same material as jeans. Is this too loose of an interpretation?? Well, I wore this to school last week and no one said anything. Actually, that's a lie, two of my colleagues commented that "the skirt is super cute." 

I'd love to know your thoughts on this denim debate. 

Total side note--I feel wicked American in this outfit. The red, white, and blue in a fun, non-American flag way. I will have to remember this for Memorial Day and/or the Fourth of July

Ps-- What do you think of the new hair cut?? Thanks to Hannah Pearson, I no longer look like a lion. I almost look like an adult!! EEK!! Love it! 

Shirt: Ann Taylor Loft

Skirt: Ann Taylor Loft

Shoes: Keds