I think that as the punishment is intended for her thighs, it's highly likely that the administrator has allowed her to keep her knickers on. I agree that she should have had at least a spanking on her backside, knickers down and modesty denied. The caning of the soft fleshy tops of the is something I witnessed a few times at school and from experience (yes, I had to try it), it stings worse than the cane on the bare backside and marks seemed to last a lot longer. I find the cane being applied to a female's thighs quite arousing.